The footprint of this particular service could have been optimized in Java but:

  1. the JVM itself imposes a high floor (hotspot, many shared libs loaded, ...)

  2. the Java language is full of overhead at every level (boxed types are a pet peeve of mine)

  3. the Java ecosystem has a tendency to regard memory as an inexhaustible resource, which lead a lot of waste in many 3rd party libraries

The core point is that optimizing this particular Java program (and the others that followed) would have been more time-consuming than a Golang rewrite and would have probably increased the complexity whereas a Golang rewrite reduced it.

Optimization was the original goal, increased maintainability was a pleasant result.