Hey,
From what I understand this is just a provisioning option in Amazon OpenSearch Service, one that should be transparent to users.
Hibernate Search is already compatible with OpenSearch since Hibernate Search 6.1, and has a dedicated module to cope with the specifics of Amazon services. So if the APIs of Amazon OpenSearch Serverless really are the same as those of “classic” Amazon OpenSearch Service, then Hibernate Search should already work with this.
That being said, this “serverless” option is primarily aimed at short-lived applications. For such applications, you will probably want to take some precautions to disable a few things in Hibernate Search, in particular schema management on startup (manage it manually instead) and version check on startup.
One thing to note for “serverless” applications, but only if you use outbox-polling coordination (which is opt-in, but can be useful for highly scalable applications). If you scale your applications down to 0, background processing of indexing events will stop, and may not have processed all events when it stops. Maybe you could make it work by inserting some custom check in your scale-down mechanics to only scale down when there are no longer any events to process. Or just by having a long enough delay before scaling down to 0, so that you’re reasonably certain all events have been processed before your application scales down. But whether you can do that at all depends on your particular setup.