Time To Live (TTL) for DynamoDB is a cost-effective method for deleting items that are no longer relevant. TTL allows you to define a per-item expiration timestamp that indicates when an item is no longer needed. DynamoDB automatically deletes expired items within a few days of their expiration time, without consuming write throughput.
To use TTL, first enable it on a table and then define a specific attribute to store the
TTL expiration timestamp. The timestamp must be stored in Unix epoch time format
Items with valid, expired TTL attributes may be deleted by the system at any time, typically within a few days of their expiration. You can still update the expired items that are pending deletion, including changing or removing their TTL attributes. While updating an expired item, we recommended that you use a condition expression to make sure the item has not been subsequently deleted. Use filter expressions to remove expired items from Scan and Query results.
Deleted items work similarly to those deleted through typical delete operations. Once deleted, items go into DynamoDB Streams as service deletions instead of user deletes, and are removed from local secondary indexes and global secondary indexes just like other delete operations.
If you are using Global Tables version 2019.11.21 (Current) of global tables and you also use the TTL feature, DynamoDB replicates TTL deletes to all replica tables. The initial TTL delete does not consume Write Capacity Units (WCU) in the region in which the TTL expiry occurs. However, the replicated TTL delete to the replica table(s) consumes a replicated Write Capacity Unit when using provisioned capacity, or Replicated Write Unit when using on-demand capacity mode, in each of the replica regions and applicable charges will apply.
For more information about TTL, see these topics:
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