Efficient upstream REST response pass-through

[jimbogithub]

Q. What is the best way to pass an upstream REST response to a downstream REST client? I'm looking for the most resource efficient approach.

Background:

Given client -> restFacade -> shardedRestService we want to produce a response in shardedRestService and have it pass through the restFacade back to the client. shardedRestService is private so a redirect is not suitable.

We had a pre Quarkus 3.25.x implementation that worked using the underlying InputStream although it had to be blocking as the InputStream had to be buffered. Since Quarkus 3.25.x it appears the buffering has been No-Op'd (https://github.com/quarkusio/quarkus/pull/48807/files#diff-3d3a89ac1de50e6e9389fa505c8ba2cfbe57234f664bd331821c6f2480361f71) so this solution no longer works (and was never ideal due to the buffering and blocking).

Post Quarkus 3.25.x we are using Uni<byte[]> as the response type for the restFacade and the REST Client API that it uses to access shardedRestService. This seems pretty good as it is non-blocking and does not need to materialise the underlying JSON data objects during the pass-through. It does presumably have to wait for the full shardedRestService response before it can start forwarding to the client and does look like it needs to create a copy of the response byte[] (from Buffer) but fortunately they are not too large. This solution gets three green ticks in the DevUI.

But is there a better way?