On 5 August 2026 DynamoDB got native vector search. The interesting part is not that DynamoDB can run similarity queries, since several AWS services already do that. It is that the embedding is an ordinary attribute on an ordinary item, so the row and the vector that represents it commit in the same PutItem. This post covers what shipped, why that single write matters, the two use cases it fits best, and what to watch before building on it. ...
Is it safe to retry? For most APIs the honest answer is no, not without work. Any request that can be retried will eventually be retried against a handler that already succeeded, and unless you have designed for it, every retry applies the operation again. The retries are not hypothetical. A client times out and sends the request a second time. API Gateway gives up at its integration timeout and returns a 504 while the Lambda behind it keeps running and commits the write anyway, a case I covered in Part 4 of the Rust on Lambda series. An SQS or event-source trigger redelivers a message because delivery is at-least-once by default. The common thread is that at-least-once delivery is what you get for free; exactly-once is something you build. This post is about building it with DynamoDB conditional writes. ...