DynamoDB Replicated Write Request Units

Amazon DynamoDB Time to Live (TTL) allows you to define a per-item timestamp to determine when an item is no longer needed. Shortly after the date and time of the specified timestamp, DynamoDB deletes the item from your table without consuming any write throughput. TTL is provided at no extra cost as a means to reduce stored data volume by retaining only the items that remain current for your workload’s needs

For DynamoDB Global Tables, TTL items are deleted free of charge in the source region, and then that delete is replicated to all other regions. This is the reason you see an increased rWCU consumption for your tables.

More here: https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/TTL.html

"If you are using Version 2019.11.21 (Current) of global tables and you also use the Time to Live feature, DynamoDB replicates TTL deletes to all replica tables. The initial TTL delete does not consume write capacity 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 when using on-demand capacity mode, in each of the replica regions and applicable charges will apply."