Comment by bashtoni
The service is still in preview, so AWS are explicitly telling people not to put it into production.
From my non-production experiments with it, the main limitation is that you can only retrieve up to 30 top_k results, which means you can't use it with a re-ranker, or at least not as effectively. For many production use cases that will be a deal breaker.
My issue with it is that it requires a lot of duplication between it and a traditional rdbms; you can’t use it alone because it doesn’t offer filtering without a search vector (i.e. what some vendors call a scroll function).