# Prefer using custom IDs for node/relationship
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 Neptune allows users to explicitly assign IDs on nodes and relationships. The ID must be globally unique in the dataset and deterministic to be useful. A deterministic ID can be used as a lookup or a filtering mechanism just like properties; however, using an ID is much more optimized from query execution perspective than using properties. There are several benefits to using custom IDs - 
+  Properties can be null for an existing entity, but the ID must exist. This allows the query engine to use an optimized join during execution. 
+  When concurrent mutation queries are executed, the chances of [ concurrent modification exceptions](https://docs.aws.amazon.com//neptune/latest/userguide/transactions-exceptions.html) (CMEs) are reduced significantly when IDs are used to access nodes because fewer locks are taking on IDs than properties due to their enforced uniqueness. 
+  Using IDs avoids the chance of creating duplicate data as Neptune enforces uniqueness on IDs, unlike properties. 

 The following query example uses a custom ID: 

**Note**  
 The property `~id` is used to specify the ID, whereas `id` is just stored as any other property. 

```
CREATE (n:Person {`~id`: '1', name: 'alice'})
```

 Without using a custom ID: 

```
CREATE (n:Person {id: '1', name: 'alice'})
```

 If using the latter mechanism, there is no uniqueness enforcement and you could later execute the query: 

```
CREATE (n:Person {id: '1', name: 'john'})
```

 This creates a second node with `id=1` named `john`. In this scenario, you would now have two nodes with `id=1`, each having a different name - (alice and john).