Swap Java and Go in text, then I buy it. Java is memory hungry monstrosity that runs on JVM and idiomatically uses piles of abstractions. I have exactly opposite experience, when rewriting a microservice from Jave to go reduced memory usage tenfold and sped up requests processing.

No, I believe it this way. It used to be one service that had access to everything it needs. Now it is microservices, so each microservice is caching a bunch of stuff, but of course all the wrong stuff, so every request requires at least one network call downstream. Thus more memory usage and slower.