# Prerequisites and limitations
Before you follow this guide, work with your AWS account team or AWS Partner to review the prerequisites and limitations for implementing edge architectures with AWS Outposts and Local Zones.
## Prerequisites
### AWS Outposts
+ Your existing data center must meet the [AWS Outposts requirements](https://docs.aws.amazon.com/outposts/latest/userguide/outposts-requirements.html) for facilities, networking, and power. AWS Outposts is designed to operate in a data center environment that has 5-15 kVA redundant power inputs, 145.8 times the kVA of cubic feet per minute (CFM) airflow, and an ambient temperature between 41° F (5° C) and 95° F (35° C), among other requirements.
+ Confirm that the AWS Outposts service is available in your country by consulting the [AWS Outposts rack FAQs](https://aws.amazon.com/outposts/rack/faqs/). See the question: *In which countries and territories is Outposts rack available?*
+ If your organization requires four or more [AWS Outposts racks](https://aws.amazon.com/outposts/rack/), your data center must meet the [Aggregation, Core, Edge (ACE) rack requirements](https://docs.aws.amazon.com/outposts/latest/userguide/outposts-ace-requirements.html).
+ An internet or AWS Direct Connect link of at least 500 Mbps (1 Gbps is better) must be provided and sustained to connect [AWS Outposts to the AWS Region](https://docs.aws.amazon.com/outposts/latest/userguide/region-connectivity.html), with appropriate backup connectivity if your use case requires it. The round-trip time latency from AWS Outposts to the Region must be 175 milliseconds at the maximum.
+ You must have an active contract for [AWS Enterprise Support](https://aws.amazon.com/premiumsupport/plans/enterprise/) or an [AWS Unified Operations](https://aws.amazon.com/premiumsupport/plans/unified-operations/) plan.
### AWS Local Zones
+ An AWS Local Zone must be available close to your data centers or users. See [AWS Local Zones locations](https://aws.amazon.com/about-aws/global-infrastructure/localzones/locations/).
+ Confirm that you have network connectivity from your on-premises infrastructure to the Local Zone:
+ Option 1: An Direct Connect link from your data center to the [Direct Connect point of presence (PoP)](https://aws.amazon.com/directconnect/locations/) that's closest to the Local Zone. For more information, see [Direct Connect](https://docs.aws.amazon.com/local-zones/latest/ug/local-zones-connectivity-direct-connect.html) in the Local Zones documentation.
+ Option 2: An internet link in addition to an on-premises virtual private network (VPN) appliance and the necessary licensing to launch a software-based VPN appliance on Amazon EC2 in the Local Zone. For more information, see [VPN connection](https://docs.aws.amazon.com/local-zones/latest/ug/local-zones-connectivity-ec2-vpn.html) in the Local Zones documentation.
For additional connectivity options, see the [Local Zones documentation](https://docs.aws.amazon.com/local-zones/latest/ug/local-zones-connectivity.html).
## Limitations
### AWS Outposts
+ Amazon Relational Database Service (Amazon RDS) on AWS Outposts Multi-AZ deployments require customer-owned IP (CoIP) address pools. For more information, see [Customer-owned IP addresses for Amazon RDS on AWS Outposts](https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/rds-on-outposts.coip.html).
+ Multi-AZ on AWS Outposts is available for all supported versions of MySQL and PostgreSQL on Amazon RDS on AWS Outposts. For more information, see [Amazon RDS on AWS Outposts support for Amazon RDS features](https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/rds-on-outposts.features.html). [Amazon RDS on AWS Outposts supports ](https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/rds-on-outposts.html)SQL Server, Amazon RDS for MySQL, and Amazon RDS for PostgreSQL databases.
+ AWS Outposts isn't designed to operate when it's disconnected from an AWS Region. For more information, see the [Thinking in terms of failure modes](https://docs.aws.amazon.com/whitepapers/latest/aws-outposts-high-availability-design/thinking-in-terms-of-failure-modes.html) section in the AWS whitepaper *AWS Outposts High Availability Design and Architecture Considerations*.
+ Amazon Simple Storage Service (Amazon S3) on AWS Outposts has some limitations. These are discussed in the [How is Amazon S3 on Outposts different from Amazon S3?](https://docs.aws.amazon.com/AmazonS3/latest/userguide/S3OnOutpostsRestrictionsLimitations.html) section of the *Amazon S3 on Outposts User Guide*.
+ Application Load Balancers on AWS Outposts don't support mutual TLS (mTLS) or sticky sessions.
+ The ACE racks aren't fully enclosed and don't include front or rear doors.
+ The instance capacity tool is applicable only for new orders.
### AWS Local Zones
+ Local Zones don't have an AWS Site-to-Site VPN endpoint. Instead, use a software-based VPN on Amazon EC2.
+ Local Zones don't support AWS Transit Gateway. Instead, connect to the Local Zone by using a Direct Connect Private virtual interface (VIF).
+ Not all Local Zones support services such as Amazon RDS, Amazon FSx, Amazon EMR, or Amazon ElastiCache, or NAT gateways. For more information, see [AWS Local Zones features](https://aws.amazon.com/about-aws/global-infrastructure/localzones/features/?nc=sn&loc=2).
+ Application Load Balancers in Local Zones don't support mTLS or sticky sessions.