DynamoDB Item Insert Limit

Question

Is there a way to limit the number of items inserted in a DynamoDB by user ID. I have an alexa skill that i want to limit the number of items added to table by the alexa user ID? Or is there a way to have DynamoDB table count the unique user ids and limit insert for each id after, for example, 5 entries? So, every unique user id can only have 5 entries.

Answer

For this you would need to keep a counter record for each item and use DynamoDB Transactions to achieve your use case. 
For each AlexaID create a record for storing counts of records:

| Pk | Sk | Items |
| --- | --- | --- |
| AlexaId | Counter | 3 |

Then you would use a [TransactWrite](https://docs.aws.amazon.com/amazondynamodb/latest/APIReference/API_TransactWriteItems.html) with a condition for each new write, and also an Update to update the counter.

```
TransactWrite:
Put - new item
Update - update counter ++
Condition - if counter record Items value < 6
```

Answer

There is not a way to have this enforced automatically. You'd have to keep a counter yourself and have your application code ensure requests were rejected that exceeded your limit.

DynamoDB Item Insert Limit

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