Well, give me a real world software example (so not a hello world thing) I can download and test and compare. I have dev & devops experience with Java, so let's take something that's used a lot; Zookeeper; Clickhouse ported it to C++ for a reason; the original sucks resources, CH Keeper you don't even notice. Maybe you will say it's written badly, but if a Apache posterchild is written badly, what does that say? Same for Apache Cassandra; even starting it for dev is a crime, let alone use it unless you have many nodes. Scylla, the C++ implementation, runs circles around a cluster of it on one box. But again, you might say it was badly done. ElasticSearch... Best not mentioned as it's a very well known resource hog vs native implementations search engines. As others said; anything Apache Spring for any real life application.

So what's a good example so I can compare it to a non Java version?