DynamoDB storage cost calculation with TTL

I'd suggest being careful about making significant assumptions about costs without testing them in practice. Documentation explains that deletion based on TTL is implemented as a background process and may take days to complete deleting an item after its expiration time. It further explains that to ensure your queries don't return items with expiration times in the past, you should apply explicit filters in your queries and scans to exclude them, further emphasising that the TTL-based deletions aren't immediate. https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/TTL.html

Therefore, I wouldn't expect the 1-hour TTL to be anywhere near one hour for either functional or pricing purposes but probably somewhere around 24-48 hours. If you're calling DeleteItem to delete your items explicitly, rather than relying on the TTL mechanism, the explicit deletions should be expected to be reflected within seconds.