# Scaling Valkey or Redis OSS (Cluster Mode Enabled) clusters As demand on your clusters changes, you might decide to improve performance or reduce costs by changing the number of shards in your Valkey or Redis OSS (cluster mode enabled) cluster. We recommend using online horizontal scaling to do so, because it allows your cluster to continue serving requests during the scaling process. Conditions under which you might decide to rescale your cluster include the following: + **Memory pressure:** If the nodes in your cluster are under memory pressure, you might decide to scale out so that you have more resources to better store data and serve requests. You can determine whether your nodes are under memory pressure by monitoring the following metrics: *FreeableMemory*, *SwapUsage*, and *BytesUsedForCache*. + **CPU or network bottleneck:** If latency/throughput issues are plaguing your cluster, you might need to scale out to resolve the issues. You can monitor your latency and throughput levels by monitoring the following metrics: *CPUUtilization*, *NetworkBytesIn*, *NetworkBytesOut*, *CurrConnections*, and *NewConnections*. + **Your cluster is over-scaled:** Current demand on your cluster is such that scaling in doesn't hurt performance and reduces your costs. You can monitor your cluster's use to determine whether or not you can safely scale in using the following metrics: *FreeableMemory*, *SwapUsage*, *BytesUsedForCache*, *CPUUtilization*, *NetworkBytesIn*, *NetworkBytesOut*, *CurrConnections*, and *NewConnections*. **Performance Impact of Scaling** When you scale using the offline process, your cluster is offline for a significant portion of the process and thus unable to serve requests. When you scale using the online method, because scaling is a compute-intensive operation, there is some degradation in performance, nevertheless, your cluster continues to serve requests throughout the scaling operation. How much degradation you experience depends upon your normal CPU utilization and your data. There are two ways to scale your Valkey or Redis OSS (cluster mode enabled) cluster; horizontal and vertical scaling. + Horizontal scaling allows you to change the number of node groups (shards) in the replication group by adding or removing node groups (shards). The online resharding process allows scaling in/out while the cluster continues serving incoming requests. Configure the slots in your new cluster differently than they were in the old cluster. Offline method only. + Vertical Scaling - Change the node type to resize the cluster. The online vertical scaling allows scaling up/down while the cluster continues serving incoming requests. If you are reducing the size and memory capacity of the cluster, by either scaling in or scaling down, ensure that the new configuration has sufficient memory for your data and Valkey or Redis OSS overhead. For more information, see [Choosing your node size](CacheNodes.SelectSize.md). **Contents** + [Offline resharding for Valkey or Redis OSS (cluster mode enabled)](#redis-cluster-resharding-offline) + [Online resharding for Valkey or Redis OSS (cluster mode enabled)](#redis-cluster-resharding-online) + [Adding shards with online resharding](#redis-cluster-resharding-online-add) + [Removing shards with online resharding](#redis-cluster-resharding-online-remove) + [Removing shards (Console)](#redis-cluster-resharding-online-remove-console) + [Removing shards (AWS CLI)](#redis-cluster-resharding-online-remove-cli) + [Removing shards (ElastiCache API)](#redis-cluster-resharding-online-remove-api) + [Online shard rebalancing](#redis-cluster-resharding-online-rebalance) + [Online Shard Rebalancing (Console)](#redis-cluster-resharding-online-rebalance-console) + [Online shard rebalancing (AWS CLI)](#redis-cluster-resharding-online-rebalance-cli) + [Online shard rebalancing (ElastiCache API)](#redis-cluster-resharding-online-rebalance-api) + [Online vertical scaling by modifying node type](redis-cluster-vertical-scaling.md) + [Online scaling up](redis-cluster-vertical-scaling.md#redis-cluster-vertical-scaling-scaling-up) + [Scaling up Valkey or Redis OSS clusters (Console)](redis-cluster-vertical-scaling.md#redis-cluster-vertical-scaling-console) + [Scaling up Valkey or Redis OSS clusters (AWS CLI)](redis-cluster-vertical-scaling.md#Scaling.RedisStandalone.ScaleUp.CLI) + [Scaling up Valkey or Redis OSS clusters (ElastiCache API)](redis-cluster-vertical-scaling.md#VeticalScaling.RedisReplGrps.ScaleUp.API) + [Online scaling down](redis-cluster-vertical-scaling.md#redis-cluster-vertical-scaling-scaling-down) + [Scaling down Valkey or Redis OSS clusters (Console)](redis-cluster-vertical-scaling.md#redis-cluster-vertical-scaling-down-console) + [Scaling down Valkey or Redis OSS clusters (AWS CLI)](redis-cluster-vertical-scaling.md#Scaling.RedisStandalone.ScaleDown.CLI) + [Scaling down Valkey or Redis OSS clusters (ElastiCache API)](redis-cluster-vertical-scaling.md#Scaling.Vertical.ScaleDown.API) ## Offline resharding for Valkey or Redis OSS (cluster mode enabled) The main advantage you get from offline shard reconfiguration is that you can do more than merely add or remove shards from your replication group. When you reshard and rebalance offline, in addition to changing the number of shards in your replication group, you can do the following: **Note** Offline resharding is not supported on Valkey or Redis OSS clusters with data tiering enabled. For more information, see [Data tiering in ElastiCache](data-tiering.md). + Change the node type of your replication group. + Specify the Availability Zone for each node in the replication group. + Upgrade to a newer engine version. + Specify the number of replica nodes in each shard independently. + Specify the keyspace for each shard. The main disadvantage of offline shard reconfiguration is that your cluster is offline beginning with the restore portion of the process and continuing until you update the endpoints in your application. The length of time that your cluster is offline varies with the amount of data in your cluster. **To reconfigure your shards Valkey or Redis OSS (cluster mode enabled) cluster offline** 1. Create a manual backup of your existing Valkey or Redis OSS cluster. For more information, see [Taking manual backups](backups-manual.md). 1. Create a new cluster by restoring from the backup. For more information, see [Restoring from a backup into a new cache](backups-restoring.md). 1. Update the endpoints in your application to the new cluster's endpoints. For more information, see [Finding connection endpoints in ElastiCache](Endpoints.md). ## Online resharding for Valkey or Redis OSS (cluster mode enabled) By using online resharding and shard rebalancing with ElastiCache Valkey 7.2 or newer, or Redis OSS version 3.2.10 or newer, you can scale your Valkey or Redis OSS (cluster mode enabled) cluster dynamically with no downtime. This approach means that your cluster can continue to serve requests even while scaling or rebalancing is in process. You can do the following: + **Scale out** – Increase read and write capacity by adding shards (node groups) to your Valkey or Redis OSS (cluster mode enabled) cluster (replication group). If you add one or more shards to your replication group, the number of nodes in each new shard is the same as the number of nodes in the smallest of the existing shards. + **Scale in** – Reduce read and write capacity, and thereby costs, by removing shards from your Valkey or Redis OSS (cluster mode enabled) cluster. + **Rebalance** – Move the keyspaces among the shards in your Valkey or Redis OSS (cluster mode enabled) cluster so they are as equally distributed among the shards as possible. You can't do the following: + **Configure shards independently:** You can't specify the keyspace for shards independently. To do this, you must use the offline process. Currently, the following limitations apply to ElastiCache online resharding and rebalancing: + These processes require Valkey 7.2 and newer or Redis OSS 3.2.10 or newer. For information on upgrading your engine version, see [Version Management for ElastiCache](VersionManagement.md). + There are limitations with slots or keyspaces and large items: If any of the keys in a shard contain a large item, that key isn't migrated to a new shard when scaling out or rebalancing. This functionality can result in unbalanced shards. If any of the keys in a shard contain a large item (items greater than 256 MB after serialization), that shard isn't deleted when scaling in. This functionality can result in some shards not being deleted. + When scaling out, the number of nodes in any new shards equals the number of nodes in the smallest existing shard. + When scaling out, any tags that are common to all existing shards are copied to the new shards. + When scaling out a Global Data Store cluster, ElastiCache will not automatically replicate Functions from one of the existing nodes to the new node(s). We recommend loading your Functions in the new shard(s) after scaling out your cluster so that every shards have the same functions. **Note** In ElastiCache for Valkey 7.2 and above, and ElastiCache for Redis OSS version 7 and above: When scaling out your cluster, ElastiCache will automatically replicate the Functions loaded in one of the existing nodes (selected at random) to the new node(s). If your application uses [Functions](https://valkey.io/topics/functions-intro/), we recommend loading all of your functions to all the shards before scaling out so that your cluster does not end up with different function definitions on different shards. For more information, see [Online cluster resizing](best-practices-online-resharding.md). You can horizontally scale or rebalance your Valkey or Redis OSS (cluster mode enabled) clusters using the AWS Management Console, the AWS CLI, and the ElastiCache API. ### Adding shards with online resharding You can add shards to your Valkey or Redis OSS (cluster mode enabled) cluster using the AWS Management Console, AWS CLI, or ElastiCache API. When you add shards to a Valkey or Redis OSS (cluster mode enabled) cluster, any tags on the existing shards are copied over to the new shards. **Topics** #### Adding shards (Console) You can use the AWS Management Console to add one or more shards to your Valkey or Redis OSS (cluster mode enabled) cluster. The following procedure describes the process. **To add shards to your Valkey or Redis OSS (cluster mode enabled) cluster** 1. Open the ElastiCache console at [https://console.aws.amazon.com/elasticache/](https://console.aws.amazon.com/elasticache/). 1. From the navigation pane, choose **Valkey clusters** or **Redis OSS clusters**. 1. Locate and choose the name, not the box to the left of the cluster's name, of the Valkey or Redis OSS (cluster mode enabled) cluster that you want to add shards to. **Tip** Valkey or Redis OSS (cluster mode enabled) show **Clustered Valkey** or **Clustered Redis OSS** in the **Mode** column 1. Choose **Add shard**. 1. For **Number of shards to be added**, choose the number of shards you want added to this cluster. 1. For **Availability zone(s)**, choose either **No preference** or **Specify availability zones**. 1. If you chose **Specify availability zones**, for each node in each shard, select the node's Availability Zone from the list of Availability Zones. 1. Choose **Add**. #### Adding shards (AWS CLI) The following process describes how to reconfigure the shards in your Valkey or Redis OSS (cluster mode enabled) cluster by adding shards using the AWS CLI. Use the following parameters with `modify-replication-group-shard-configuration`. **Parameters** + `--apply-immediately` – Required. Specifies the shard reconfiguration operation is to be started immediately. + `--replication-group-id` – Required. Specifies which replication group (cluster) the shard reconfiguration operation is to be performed on. + `--node-group-count` – Required. Specifies the number of shards (node groups) to exist when the operation is completed. When adding shards, the value of `--node-group-count` must be greater than the current number of shards. Optionally, you can specify the Availability Zone for each node in the replication group using `--resharding-configuration`. + `--resharding-configuration` – Optional. A list of preferred Availability Zones for each node in each shard in the replication group. Use this parameter only if the value of `--node-group-count` is greater than the current number of shards. If this parameter is omitted when adding shards, Amazon ElastiCache selects the Availability Zones for the new nodes. The following example reconfigures the keyspaces over four shards in a Valkey or Redis OSS (cluster mode enabled) cluster named `my-cluster`. The example also specifies the Availability Zone for each node in each shard. The operation begins immediately. **Example - Adding Shards** For Linux, macOS, or Unix: ``` aws elasticache modify-replication-group-shard-configuration \ --replication-group-id my-cluster \ --node-group-count 4 \ --resharding-configuration \ "PreferredAvailabilityZones=us-east-2a,us-east-2c" \ "PreferredAvailabilityZones=us-east-2b,us-east-2a" \ "PreferredAvailabilityZones=us-east-2c,us-east-2d" \ "PreferredAvailabilityZones=us-east-2d,us-east-2c" \ --apply-immediately ``` For Windows: ``` aws elasticache modify-replication-group-shard-configuration ^ --replication-group-id my-cluster ^ --node-group-count 4 ^ --resharding-configuration ^ "PreferredAvailabilityZones=us-east-2a,us-east-2c" ^ "PreferredAvailabilityZones=us-east-2b,us-east-2a" ^ "PreferredAvailabilityZones=us-east-2c,us-east-2d" ^ "PreferredAvailabilityZones=us-east-2d,us-east-2c" ^ --apply-immediately ``` For more information, see [modify-replication-group-shard-configuration](https://docs.aws.amazon.com/cli/latest/reference/elasticache/modify-replication-group-shard-configuration.html) in the AWS CLI documentation. #### Adding shards (ElastiCache API) You can use the ElastiCache API to reconfigure the shards in your Valkey or Redis OSS (cluster mode enabled) cluster online by using the `ModifyReplicationGroupShardConfiguration` operation. Use the following parameters with `ModifyReplicationGroupShardConfiguration`. **Parameters** + `ApplyImmediately=true` – Required. Specifies the shard reconfiguration operation is to be started immediately. + `ReplicationGroupId` – Required. Specifies which replication group (cluster) the shard reconfiguration operation is to be performed on. + `NodeGroupCount` – Required. Specifies the number of shards (node groups) to exist when the operation is completed. When adding shards, the value of `NodeGroupCount` must be greater than the current number of shards. Optionally, you can specify the Availability Zone for each node in the replication group using `ReshardingConfiguration`. + `ReshardingConfiguration` – Optional. A list of preferred Availability Zones for each node in each shard in the replication group. Use this parameter only if the value of `NodeGroupCount` is greater than the current number of shards. If this parameter is omitted when adding shards, Amazon ElastiCache selects the Availability Zones for the new nodes. The following process describes how to reconfigure the shards in your Valkey or Redis OSS (cluster mode enabled) cluster by adding shards using the ElastiCache API. **Example - Adding Shards** The following example adds node groups to the Valkey or Redis OSS (cluster mode enabled) cluster `my-cluster`, so there are a total of four node groups when the operation completes. The example also specifies the Availability Zone for each node in each shard. The operation begins immediately. ``` https://elasticache.us-east-2.amazonaws.com/ ?Action=ModifyReplicationGroupShardConfiguration &ApplyImmediately=true &NodeGroupCount=4 &ReplicationGroupId=my-cluster &ReshardingConfiguration.ReshardingConfiguration.1.PreferredAvailabilityZones.AvailabilityZone.1=us-east-2a &ReshardingConfiguration.ReshardingConfiguration.1.PreferredAvailabilityZones.AvailabilityZone.2=us-east-2c &ReshardingConfiguration.ReshardingConfiguration.2.PreferredAvailabilityZones.AvailabilityZone.1=us-east-2b &ReshardingConfiguration.ReshardingConfiguration.2.PreferredAvailabilityZones.AvailabilityZone.2=us-east-2a &ReshardingConfiguration.ReshardingConfiguration.3.PreferredAvailabilityZones.AvailabilityZone.1=us-east-2c &ReshardingConfiguration.ReshardingConfiguration.3.PreferredAvailabilityZones.AvailabilityZone.2=us-east-2d &ReshardingConfiguration.ReshardingConfiguration.4.PreferredAvailabilityZones.AvailabilityZone.1=us-east-2d &ReshardingConfiguration.ReshardingConfiguration.4.PreferredAvailabilityZones.AvailabilityZone.2=us-east-2c &Version=2015-02-02 &SignatureVersion=4 &SignatureMethod=HmacSHA256 &Timestamp=20171002T192317Z &X-Amz-Credential= ``` For more information, see [ModifyReplicationGroupShardConfiguration](https://docs.aws.amazon.com/AmazonElastiCache/latest/APIReference/API_ModifyReplicationGroupShardConfiguration.html) in the ElastiCache API Reference. ### Removing shards with online resharding You can remove shards from your Valkey or Redis OSS (cluster mode enabled) cluster using the AWS Management Console, AWS CLI, or ElastiCache API. **Topics** + [Removing shards (Console)](#redis-cluster-resharding-online-remove-console) + [Removing shards (AWS CLI)](#redis-cluster-resharding-online-remove-cli) + [Removing shards (ElastiCache API)](#redis-cluster-resharding-online-remove-api) #### Removing shards (Console) The following process describes how to reconfigure the shards in your Valkey or Redis OSS (cluster mode enabled) cluster by removing shards using the AWS Management Console. Before removing node groups (shards) from your replication group, ElastiCache makes sure that all your data will fit in the remaining shards. If the data will fit, the specified shards are deleted from the replication group as requested. If the data won't fit in the remaining node groups, the process is terminated and the replication group is left with the same node group configuration as before the request was made. You can use the AWS Management Console to remove one or more shards from your Valkey or Redis OSS (cluster mode enabled) cluster. You cannot remove all the shards in a replication group. Instead, you must delete the replication group. For more information, see [Deleting a replication group](Replication.DeletingRepGroup.md). The following procedure describes the process for deleting one or more shards. **To remove shards from your Valkey or Redis OSS (cluster mode enabled) cluster** 1. Open the ElastiCache console at [https://console.aws.amazon.com/elasticache/](https://console.aws.amazon.com/elasticache/). 1. From the navigation pane, choose **Valkey clusters** or **Redis OSS clusters**. 1. Locate and choose the name, not the box to the left of the cluster's name, of the Valkey or Redis OSS (cluster mode enabled) cluster you want to remove shards from. **Tip** Valkey or Redis OSS (cluster mode enabled) clusters have a value of 1 or greater in the **Shards** column. 1. From the list of shards, choose the box to the left of the name of each shard that you want to delete. 1. Choose **Delete shard**. #### Removing shards (AWS CLI) The following process describes how to reconfigure the shards in your Valkey or Redis OSS (cluster mode enabled) cluster by removing shards using the AWS CLI. **Important** Before removing node groups (shards) from your replication group, ElastiCache makes sure that all your data will fit in the remaining shards. If the data will fit, the specified shards (`--node-groups-to-remove`) are deleted from the replication group as requested and their keyspaces mapped into the remaining shards. If the data will not fit in the remaining node groups, the process is terminated and the replication group is left with the same node group configuration as before the request was made. You can use the AWS CLI to remove one or more shards from your Valkey or Redis OSS (cluster mode enabled) cluster. You cannot remove all the shards in a replication group. Instead, you must delete the replication group. For more information, see [Deleting a replication group](Replication.DeletingRepGroup.md). Use the following parameters with `modify-replication-group-shard-configuration`. **Parameters** + `--apply-immediately` – Required. Specifies the shard reconfiguration operation is to be started immediately. + `--replication-group-id` – Required. Specifies which replication group (cluster) the shard reconfiguration operation is to be performed on. + `--node-group-count` – Required. Specifies the number of shards (node groups) to exist when the operation is completed. When removing shards, the value of `--node-group-count` must be less than the current number of shards. + `--node-groups-to-remove` – Required when `--node-group-count` is less than the current number of node groups (shards). A list of shard (node group) IDs to remove from the replication group. The following procedure describes the process for deleting one or more shards. **Example - Removing Shards** The following example removes two node groups from the Valkey or Redis OSS (cluster mode enabled) cluster `my-cluster`, so there are a total of two node groups when the operation completes. The keyspaces from the removed shards are distributed evenly over the remaining shards. For Linux, macOS, or Unix: ``` aws elasticache modify-replication-group-shard-configuration \ --replication-group-id my-cluster \ --node-group-count 2 \ --node-groups-to-remove "0002" "0003" \ --apply-immediately ``` For Windows: ``` aws elasticache modify-replication-group-shard-configuration ^ --replication-group-id my-cluster ^ --node-group-count 2 ^ --node-groups-to-remove "0002" "0003" ^ --apply-immediately ``` #### Removing shards (ElastiCache API) You can use the ElastiCache API to reconfigure the shards in your Valkey or Redis OSS (cluster mode enabled) cluster online by using the `ModifyReplicationGroupShardConfiguration` operation. The following process describes how to reconfigure the shards in your Valkey or Redis OSS (cluster mode enabled) cluster by removing shards using the ElastiCache API. **Important** Before removing node groups (shards) from your replication group, ElastiCache makes sure that all your data will fit in the remaining shards. If the data will fit, the specified shards (`NodeGroupsToRemove`) are deleted from the replication group as requested and their keyspaces mapped into the remaining shards. If the data will not fit in the remaining node groups, the process is terminated and the replication group is left with the same node group configuration as before the request was made. You can use the ElastiCache API to remove one or more shards from your Valkey or Redis OSS (cluster mode enabled) cluster. You cannot remove all the shards in a replication group. Instead, you must delete the replication group. For more information, see [Deleting a replication group](Replication.DeletingRepGroup.md). Use the following parameters with `ModifyReplicationGroupShardConfiguration`. **Parameters** + `ApplyImmediately=true` – Required. Specifies the shard reconfiguration operation is to be started immediately. + `ReplicationGroupId` – Required. Specifies which replication group (cluster) the shard reconfiguration operation is to be performed on. + `NodeGroupCount` – Required. Specifies the number of shards (node groups) to exist when the operation is completed. When removing shards, the value of `NodeGroupCount` must be less than the current number of shards. + `NodeGroupsToRemove` – Required when `--node-group-count` is less than the current number of node groups (shards). A list of shard (node group) IDs to remove from the replication group. The following procedure describes the process for deleting one or more shards. **Example - Removing Shards** The following example removes two node groups from the Valkey or Redis OSS (cluster mode enabled) cluster `my-cluster`, so there are a total of two node groups when the operation completes. The keyspaces from the removed shards are distributed evenly over the remaining shards. ``` https://elasticache.us-east-2.amazonaws.com/ ?Action=ModifyReplicationGroupShardConfiguration &ApplyImmediately=true &NodeGroupCount=2 &ReplicationGroupId=my-cluster &NodeGroupsToRemove.member.1=0002 &NodeGroupsToRemove.member.2=0003 &Version=2015-02-02 &SignatureVersion=4 &SignatureMethod=HmacSHA256 &Timestamp=20171002T192317Z &X-Amz-Credential= ``` ### Online shard rebalancing You can rebalance shards in your Valkey or Redis OSS (cluster mode enabled) cluster using the AWS Management Console, AWS CLI, or ElastiCache API. **Topics** + [Online Shard Rebalancing (Console)](#redis-cluster-resharding-online-rebalance-console) + [Online shard rebalancing (AWS CLI)](#redis-cluster-resharding-online-rebalance-cli) + [Online shard rebalancing (ElastiCache API)](#redis-cluster-resharding-online-rebalance-api) #### Online Shard Rebalancing (Console) The following process describes how to reconfigure the shards in your Valkey or Redis OSS (cluster mode enabled) cluster by rebalancing shards using the AWS Management Console. **To rebalance the keyspaces among the shards on your Valkey or Redis OSS (cluster mode enabled) cluster** 1. Open the ElastiCache console at [https://console.aws.amazon.com/elasticache/](https://console.aws.amazon.com/elasticache/). 1. From the navigation pane, choose **Valkey clusters** or **Redis OSS clusters**. 1. Choose the name, not the box to the left of the name, of the Valkey or Redis OSS (cluster mode enabled) cluster that you want to rebalance. **Tip** Valkey or Redis OSS (cluster mode enabled) clusters have a value of 1 or greater in the **Shards** column. 1. Choose **Rebalance**. 1. When prompted, choose **Rebalance**. You might see a message similar to this one: *Slots in the replication group are uniformly distributed. Nothing to do. (Service: AmazonElastiCache; Status Code: 400; Error Code: InvalidReplicationGroupState; Request ID: 2246cebd-9721-11e7-8d5b-e1b0f086c8cf)*. If you do, choose **Cancel**. #### Online shard rebalancing (AWS CLI) Use the following parameters with `modify-replication-group-shard-configuration`. **Parameters** + `-apply-immediately` – Required. Specifies the shard reconfiguration operation is to be started immediately. + `--replication-group-id` – Required. Specifies which replication group (cluster) the shard reconfiguration operation is to be performed on. + `--node-group-count` – Required. To rebalance the keyspaces across all shards in the cluster, this value must be the same as the current number of shards. The following process describes how to reconfigure the shards in your Valkey or Redis OSS (cluster mode enabled) cluster by rebalancing shards using the AWS CLI. **Example - Rebalancing the Shards in a Cluster** The following example rebalances the slots in the Valkey or Redis OSS (cluster mode enabled) cluster `my-cluster` so that the slots are distributed as equally as possible. The value of `--node-group-count` (`4`) is the number of shards currently in the cluster. For Linux, macOS, or Unix: ``` aws elasticache modify-replication-group-shard-configuration \ --replication-group-id my-cluster \ --node-group-count 4 \ --apply-immediately ``` For Windows: ``` aws elasticache modify-replication-group-shard-configuration ^ --replication-group-id my-cluster ^ --node-group-count 4 ^ --apply-immediately ``` #### Online shard rebalancing (ElastiCache API) You can use the ElastiCache API to reconfigure the shards in your Valkey or Redis OSS (cluster mode enabled) cluster online by using the `ModifyReplicationGroupShardConfiguration` operation. Use the following parameters with `ModifyReplicationGroupShardConfiguration`. **Parameters** + `ApplyImmediately=true` – Required. Specifies the shard reconfiguration operation is to be started immediately. + `ReplicationGroupId` – Required. Specifies which replication group (cluster) the shard reconfiguration operation is to be performed on. + `NodeGroupCount` – Required. To rebalance the keyspaces across all shards in the cluster, this value must be the same as the current number of shards. The following process describes how to reconfigure the shards in your Valkey or Redis OSS (cluster mode enabled) cluster by rebalancing the shards using the ElastiCache API. **Example - Rebalancing a Cluster** The following example rebalances the slots in the Valkey or Redis OSS (cluster mode enabled) cluster `my-cluster` so that the slots are distributed as equally as possible. The value of `NodeGroupCount` (`4`) is the number of shards currently in the cluster. ``` https://elasticache.us-east-2.amazonaws.com/ ?Action=ModifyReplicationGroupShardConfiguration &ApplyImmediately=true &NodeGroupCount=4 &ReplicationGroupId=my-cluster &Version=2015-02-02 &SignatureVersion=4 &SignatureMethod=HmacSHA256 &Timestamp=20171002T192317Z &X-Amz-Credential= ``` # Online vertical scaling by modifying node type By using online vertical scaling with Valkey version 7.2 or newer, or Redis OSS version 3.2.10 or newer, you can scale your Valkey or Redis OSS clusters dynamically with minimal downtime. This allows your Valkey or Redis OSS cluster to serve requests even while scaling. **Note** Scaling is not supported between a data tiering cluster (for example, a cluster using an r6gd node type) and a cluster that does not use data tiering (for example, a cluster using an r6g node type). For more information, see [Data tiering in ElastiCache](data-tiering.md). You can do the following: + **Scale up** – Increase read and write capacity by adjusting the node type of your Valkey or Redis OSS cluster to use a larger node type. ElastiCache dynamically resizes your cluster while remaining online and serving requests. + **Scale down** – Reduce read and write capacity by adjusting the node type down to use a smaller node. Again, ElastiCache dynamically resizes your cluster while remaining online and serving requests. In this case, you reduce costs by downsizing the node. **Note** The scale up and scale down processes rely on creating clusters with newly selected node types and synchronizing the new nodes with the previous ones. To ensure a smooth scale up/down flow, do the following: Ensure you have sufficient ENI (Elastic Network Interface) capacity. If scaling down, ensure the smaller node has sufficient memory to absorb expected traffic. For best practices on memory management, see [Managing reserved memory for Valkey and Redis OSS](redis-memory-management.md). While the vertical scaling process is designed to remain fully online, it does rely on synchronizing data between the old node and the new node. We recommend that you initiate scale up/down during hours when you expect data traffic to be at its minimum. Test your application behavior during scaling in a staging environment, if possible. **Contents** + [Online scaling up](#redis-cluster-vertical-scaling-scaling-up) + [Scaling up Valkey or Redis OSS clusters (Console)](#redis-cluster-vertical-scaling-console) + [Scaling up Valkey or Redis OSS clusters (AWS CLI)](#Scaling.RedisStandalone.ScaleUp.CLI) + [Scaling up Valkey or Redis OSS clusters (ElastiCache API)](#VeticalScaling.RedisReplGrps.ScaleUp.API) + [Online scaling down](#redis-cluster-vertical-scaling-scaling-down) + [Scaling down Valkey or Redis OSS clusters (Console)](#redis-cluster-vertical-scaling-down-console) + [Scaling down Valkey or Redis OSS clusters (AWS CLI)](#Scaling.RedisStandalone.ScaleDown.CLI) + [Scaling down Valkey or Redis OSS clusters (ElastiCache API)](#Scaling.Vertical.ScaleDown.API) ## Online scaling up **Topics** + [Scaling up Valkey or Redis OSS clusters (Console)](#redis-cluster-vertical-scaling-console) + [Scaling up Valkey or Redis OSS clusters (AWS CLI)](#Scaling.RedisStandalone.ScaleUp.CLI) + [Scaling up Valkey or Redis OSS clusters (ElastiCache API)](#VeticalScaling.RedisReplGrps.ScaleUp.API) ### Scaling up Valkey or Redis OSS clusters (Console) The following procedure describes how to scale up a Valkey or Redis OSS cluster using the ElastiCache Management Console. During this process, your cluster will continue to serve requests with minimal downtime. **To scale up a Valkey or Redis OSS cluster (console)** 1. Sign in to the AWS Management Console and open the ElastiCache console at [ https://console.aws.amazon.com/elasticache/](https://console.aws.amazon.com/elasticache/). 1. From the navigation pane, choose **Valkey clusters** or **Redis OSS clusters**. 1. From the list of clusters, choose the cluster. 1. Choose **Modify**. 1. In the **Modify Cluster** wizard: 1. Choose the node type you want to scale to from the **Node type** list. To scale up, select a node type larger than your existing node. 1. If you want to perform the scale-up process right away, choose the **Apply immediately** box. If the **Apply immediately** box is not chosen, the scale-up process is performed during this cluster's next maintenance window. 1. Choose **Modify**. If you chose **Apply immediately** in the previous step, the cluster's status changes to *modifying*. When the status changes to *available*, the modification is complete and you can begin using the new cluster. ### Scaling up Valkey or Redis OSS clusters (AWS CLI) The following procedure describes how to scale up a Valkey or Redis OSS cluster using the AWS CLI. During this process, your cluster will continue to serve requests with minimal downtime. **To scale up a Valkey or Redis OSS cluster (AWS CLI)** 1. Determine the node types you can scale up to by running the AWS CLI `list-allowed-node-type-modifications` command with the following parameter. For Linux, macOS, or Unix: ``` aws elasticache list-allowed-node-type-modifications \ --replication-group-id my-replication-group-id ``` For Windows: ``` aws elasticache list-allowed-node-type-modifications ^ --replication-group-id my-replication-group-id ``` Output from the above command looks something like this (JSON format). ``` { "ScaleUpModifications": [ "cache.m3.2xlarge", "cache.m3.large", "cache.m3.xlarge", "cache.m4.10xlarge", "cache.m4.2xlarge", "cache.m4.4xlarge", "cache.m4.large", "cache.m4.xlarge", "cache.r3.2xlarge", "cache.r3.4xlarge", "cache.r3.8xlarge", "cache.r3.large", "cache.r3.xlarge" ] "ScaleDownModifications": [ "cache.t2.micro", "cache.t2.small ", "cache.t2.medium", "cache.t1.small " ], } ``` For more information, see [list-allowed-node-type-modifications](https://docs.aws.amazon.com/cli/latest/reference/elasticache/list-allowed-node-type-modifications.html) in the *AWS CLI Reference*. 1. Modify your replication group to scale up to the new, larger node type, using the AWS CLI `modify-replication-group` command and the following parameters. + `--replication-group-id` – The name of the replication group you are scaling up to. + `--cache-node-type` – The new node type you want to scale the cluster. This value must be one of the node types returned by the `list-allowed-node-type-modifications` command in step 1. + `--cache-parameter-group-name` – [Optional] Use this parameter if you are using `reserved-memory` to manage your cluster's reserved memory. Specify a custom cache parameter group that reserves the correct amount of memory for your new node type. If you are using `reserved-memory-percent` you can omit this parameter. + `--apply-immediately` – Causes the scale-up process to be applied immediately. To postpone the scale-up process to the cluster's next maintenance window, use the `--no-apply-immediately` parameter. For Linux, macOS, or Unix: ``` aws elasticache modify-replication-group \ --replication-group-id my-redis-cluster \ --cache-node-type cache.m3.xlarge \ --apply-immediately ``` For Windows: ``` aws elasticache modify-replication-group ^ --replication-group-id my-redis-cluster ^ --cache-node-type cache.m3.xlarge ^ --apply-immediately ``` Output from the above command looks something like this (JSON format). ``` { "ReplicationGroup": { "Status": "modifying", "Description": "my-redis-cluster", "NodeGroups": [ { "Status": "modifying", "Slots": "0-16383", "NodeGroupId": "0001", "NodeGroupMembers": [ { "PreferredAvailabilityZone": "us-east-1f", "CacheNodeId": "0001", "CacheClusterId": "my-redis-cluster-0001-001" }, { "PreferredAvailabilityZone": "us-east-1d", "CacheNodeId": "0001", "CacheClusterId": "my-redis-cluster-0001-002" } ] } ], "ConfigurationEndpoint": { "Port": 6379, "Address": "my-redis-cluster.r7gdfi.clustercfg.use1.cache.amazonaws.com" }, "ClusterEnabled": true, "ReplicationGroupId": "my-redis-cluster", "SnapshotRetentionLimit": 1, "AutomaticFailover": "enabled", "SnapshotWindow": "07:30-08:30", "MemberClusters": [ "my-redis-cluster-0001-001", "my-redis-cluster-0001-002" ], "CacheNodeType": "cache.m3.xlarge", "DataTiering": "disabled" "PendingModifiedValues": {} } } ``` For more information, see [modify-replication-group](https://docs.aws.amazon.com/cli/latest/reference/elasticache/modify-replication-group.html) in the *AWS CLI Reference*. 1. If you used the `--apply-immediately`, check the status of the cluster using the AWS CLI `describe-cache-clusters` command with the following parameter. When the status changes to *available*, you can begin using the new, larger cluster node. ### Scaling up Valkey or Redis OSS clusters (ElastiCache API) The following process scales your cluster from its current node type to a new, larger node type using the ElastiCache API. During this process, ElastiCache updates the DNS entries so they point to the new nodes. Because of this you don't have to update the endpoints in your application. For Valkey 7.2 and above Redis OSS 5.0.5 and above, you can scale auto failover enabled clusters while the cluster continues to stay online and serve incoming requests. On version Redis OSS 4.0.10 and below, you may notice a brief interruption of reads and writes on previous versions from the primary node while the DNS entry is updated.. The amount of time it takes to scale up to a larger node type varies, depending upon your node type and the amount of data in your current cluster. **To scale up a Valkey or Redis OSS Cache Cluster (ElastiCache API)** 1. Determine which node types you can scale up to using the ElastiCache API `ListAllowedNodeTypeModifications` action with the following parameter. + `ReplicationGroupId` – the name of the replication group. Use this parameter to describe a specific replication group rather than all replication groups. ``` https://elasticache.us-west-2.amazonaws.com/ ?Action=ListAllowedNodeTypeModifications &ReplicationGroupId=MyReplGroup &Version=2015-02-02 &SignatureVersion=4 &SignatureMethod=HmacSHA256 &Timestamp=20150202T192317Z &X-Amz-Credential= ``` For more information, see [ListAllowedNodeTypeModifications](https://docs.aws.amazon.com/AmazonElastiCache/latest/APIReference/API_ListAllowedNodeTypeModifications.html) in the *Amazon ElastiCache API Reference*. 1. Scale your current replication group up to the new node type using the `ModifyReplicationGroup` ElastiCache API action and with the following parameters. + `ReplicationGroupId` – the name of the replication group. + `CacheNodeType` – the new, larger node type of the clusters in this replication group. This value must be one of the instance types returned by the `ListAllowedNodeTypeModifications` action in the previous step. + `CacheParameterGroupName` – [Optional] Use this parameter if you are using `reserved-memory` to manage your cluster's reserved memory. Specify a custom cache parameter group that reserves the correct amount of memory for your new node type. If you are using `reserved-memory-percent` you can omit this parameter. + `ApplyImmediately` – Set to `true` to causes the scale-up process to be applied immediately. To postpone the scale-up process to the next maintenance window, use `ApplyImmediately``=false`. ``` https://elasticache.us-west-2.amazonaws.com/ ?Action=ModifyReplicationGroup &ApplyImmediately=true &CacheNodeType=cache.m3.2xlarge &CacheParameterGroupName=redis32-m3-2xl &ReplicationGroupId=myReplGroup &SignatureVersion=4 &SignatureMethod=HmacSHA256 &Timestamp=20141201T220302Z &Version=2014-12-01 &X-Amz-Algorithm=&AWS;4-HMAC-SHA256 &X-Amz-Date=20141201T220302Z &X-Amz-SignedHeaders=Host &X-Amz-Expires=20141201T220302Z &X-Amz-Credential= &X-Amz-Signature= ``` For more information, see [ModifyReplicationGroup](https://docs.aws.amazon.com/AmazonElastiCache/latest/APIReference/API_ModifyReplicationGroup.html) in the *Amazon ElastiCache API Reference*. 1. If you used `ApplyImmediately``=true`, monitor the status of the replication group using the ElastiCache API `DescribeReplicationGroups` action with the following parameters. When the status changes from *modifying* to *available*, you can begin writing to your new, scaled up replication group. + `ReplicationGroupId` – the name of the replication group. Use this parameter to describe a particular replication group rather than all replication groups. ``` https://elasticache.us-west-2.amazonaws.com/ ?Action=DescribeReplicationGroups &ReplicationGroupId=MyReplGroup &Version=2015-02-02 &SignatureVersion=4 &SignatureMethod=HmacSHA256 &Timestamp=20150202T192317Z &X-Amz-Credential= ``` For more information, see [DescribeReplicationGroups](https://docs.aws.amazon.com/AmazonElastiCache/latest/APIReference/API_DescribeReplicationGroups.html) in the *Amazon ElastiCache API Reference*. ## Online scaling down **Topics** + [Scaling down Valkey or Redis OSS clusters (Console)](#redis-cluster-vertical-scaling-down-console) + [Scaling down Valkey or Redis OSS clusters (AWS CLI)](#Scaling.RedisStandalone.ScaleDown.CLI) + [Scaling down Valkey or Redis OSS clusters (ElastiCache API)](#Scaling.Vertical.ScaleDown.API) ### Scaling down Valkey or Redis OSS clusters (Console) The following procedure describes how to scale down a Valkey or Redis OSS cluster using the ElastiCache Management Console. During this process, your Valkey or Redis OSS cluster will continue to serve requests with minimal downtime. **To scale Down a Valkey or Redis OSS cluster (console)** 1. Sign in to the AWS Management Console and open the ElastiCache console at [ https://console.aws.amazon.com/elasticache/](https://console.aws.amazon.com/elasticache/). 1. From the navigation pane, choose **Valkey clusters** or **Redis OSS clusters**. 1. From the list of clusters, choose your preferred cluster. 1. Choose **Modify**. 1. In the **Modify Cluster** wizard: 1. Choose the node type you want to scale to from the **Node type** list. To scale down, select a node type smaller than your existing node. Note that not all node types are available to scale down to. 1. If you want to perform the scale down process right away, choose the **Apply immediately** box. If the **Apply immediately** box is not chosen, the scale-down process is performed during this cluster's next maintenance window. 1. Choose **Modify**. If you chose **Apply immediately** in the previous step, the cluster's status changes to *modifying*. When the status changes to *available*, the modification is complete and you can begin using the new cluster. ### Scaling down Valkey or Redis OSS clusters (AWS CLI) The following procedure describes how to scale down a Valkey or Redis OSS cluster using the AWS CLI. During this process, your cluster will continue to serve requests with minimal downtime. **To scale down a Valkey or Redis OSS cluster (AWS CLI)** 1. Determine the node types you can scale down to by running the AWS CLI `list-allowed-node-type-modifications` command with the following parameter. For Linux, macOS, or Unix: ``` aws elasticache list-allowed-node-type-modifications \ --replication-group-id my-replication-group-id ``` For Windows: ``` aws elasticache list-allowed-node-type-modifications ^ --replication-group-id my-replication-group-id ``` Output from the above command looks something like this (JSON format). ``` { "ScaleUpModifications": [ "cache.m3.2xlarge", "cache.m3.large", "cache.m3.xlarge", "cache.m4.10xlarge", "cache.m4.2xlarge", "cache.m4.4xlarge", "cache.m4.large", "cache.m4.xlarge", "cache.r3.2xlarge", "cache.r3.4xlarge", "cache.r3.8xlarge", "cache.r3.large", "cache.r3.xlarge" ] "ScaleDownModifications": [ "cache.t2.micro", "cache.t2.small ", "cache.t2.medium ", "cache.t1.small" ] } ``` For more information, see [list-allowed-node-type-modifications](https://docs.aws.amazon.com/cli/latest/reference/elasticache/list-allowed-node-type-modifications.html) in the *AWS CLI Reference*. 1. Modify your replication group to scale down to the new, smaller node type, using the AWS CLI `modify-replication-group` command and the following parameters. + `--replication-group-id` – The name of the replication group you are scaling down to. + `--cache-node-type` – The new node type you want to scale the cluster. This value must be one of the node types returned by the `list-allowed-node-type-modifications` command in step 1. + `--cache-parameter-group-name` – [Optional] Use this parameter if you are using `reserved-memory` to manage your cluster's reserved memory. Specify a custom cache parameter group that reserves the correct amount of memory for your new node type. If you are using `reserved-memory-percent` you can omit this parameter. + `--apply-immediately` – Causes the scale-up process to be applied immediately. To postpone the scale-down process to the cluster's next maintenance window, use the `--no-apply-immediately` parameter. For Linux, macOS, or Unix: ``` aws elasticache modify-replication-group \ --replication-group-id my-redis-cluster \ --cache-node-type cache.t2.micro \ --apply-immediately ``` For Windows: ``` aws elasticache modify-replication-group ^ --replication-group-id my-redis-cluster ^ --cache-node-type cache.t2.micro ^ --apply-immediately ``` Output from the above command looks something like this (JSON format). ``` { "ReplicationGroup": { "Status": "modifying", "Description": "my-redis-cluster", "NodeGroups": [ { "Status": "modifying", "Slots": "0-16383", "NodeGroupId": "0001", "NodeGroupMembers": [ { "PreferredAvailabilityZone": "us-east-1f", "CacheNodeId": "0001", "CacheClusterId": "my-redis-cluster-0001-001" }, { "PreferredAvailabilityZone": "us-east-1d", "CacheNodeId": "0001", "CacheClusterId": "my-redis-cluster-0001-002" } ] } ], "ConfigurationEndpoint": { "Port": 6379, "Address": "my-redis-cluster.r7gdfi.clustercfg.use1.cache.amazonaws.com" }, "ClusterEnabled": true, "ReplicationGroupId": "my-redis-cluster", "SnapshotRetentionLimit": 1, "AutomaticFailover": "enabled", "SnapshotWindow": "07:30-08:30", "MemberClusters": [ "my-redis-cluster-0001-001", "my-redis-cluster-0001-002" ], "CacheNodeType": "cache.t2.micro", "DataTiering": "disabled" "PendingModifiedValues": {} } } ``` For more information, see [modify-replication-group](https://docs.aws.amazon.com/cli/latest/reference/elasticache/modify-replication-group.html) in the *AWS CLI Reference*. 1. If you used the `--apply-immediately`, check the status of the cluster using the AWS CLI `describe-cache-clusters` command with the following parameter. When the status changes to *available*, you can begin using the new, smaller cluster node. ### Scaling down Valkey or Redis OSS clusters (ElastiCache API) The following process scales your replication group from its current node type to a new, smaller node type using the ElastiCache API. During this process, your Valkey or Redis OSS cluster will continue to serve requests with minimal downtime. The amount of time it takes to scale down to a smaller node type varies, depending upon your node type and the amount of data in your current cluster. **Scaling down (ElastiCache API)** 1. Determine which node types you can scale down to using the ElastiCache API `ListAllowedNodeTypeModifications` action with the following parameter. + `ReplicationGroupId` – the name of the replication group. Use this parameter to describe a specific replication group rather than all replication groups. ``` https://elasticache.us-west-2.amazonaws.com/ ?Action=ListAllowedNodeTypeModifications &ReplicationGroupId=MyReplGroup &Version=2015-02-02 &SignatureVersion=4 &SignatureMethod=HmacSHA256 &Timestamp=20150202T192317Z &X-Amz-Credential= ``` For more information, see [ListAllowedNodeTypeModifications](https://docs.aws.amazon.com/AmazonElastiCache/latest/APIReference/API_ListAllowedNodeTypeModifications.html) in the *Amazon ElastiCache API Reference*. 1. Scale your current replication group down to the new node type using the `ModifyReplicationGroup` ElastiCache API action and with the following parameters. + `ReplicationGroupId` – the name of the replication group. + `CacheNodeType` – the new, smaller node type of the clusters in this replication group. This value must be one of the instance types returned by the `ListAllowedNodeTypeModifications` action in the previous step. + `CacheParameterGroupName` – [Optional] Use this parameter if you are using `reserved-memory` to manage your cluster's reserved memory. Specify a custom cache parameter group that reserves the correct amount of memory for your new node type. If you are using `reserved-memory-percent` you can omit this parameter. + `ApplyImmediately` – Set to `true` to causes the scale-down process to be applied immediately. To postpone the scale-down process to the next maintenance window, use `ApplyImmediately``=false`. ``` https://elasticache.us-west-2.amazonaws.com/ ?Action=ModifyReplicationGroup &ApplyImmediately=true &CacheNodeType=cache.t2.micro &CacheParameterGroupName=redis32-m3-2xl &ReplicationGroupId=myReplGroup &SignatureVersion=4 &SignatureMethod=HmacSHA256 &Timestamp=20141201T220302Z &Version=2014-12-01 &X-Amz-Algorithm=&AWS;4-HMAC-SHA256 &X-Amz-Date=20141201T220302Z &X-Amz-SignedHeaders=Host &X-Amz-Expires=20141201T220302Z &X-Amz-Credential= &X-Amz-Signature= ``` For more information, see [ModifyReplicationGroup](https://docs.aws.amazon.com/AmazonElastiCache/latest/APIReference/API_ModifyReplicationGroup.html) in the *Amazon ElastiCache API Reference*.