C is significantly slower at concurrency when implemented naively. It's as fast as languages like Go when implemented using the same techniques, which is not obvious and trivial to use like in a higher level GC'd language. GC actually helps out a ton there, for example look at the complexity of async/await in Rust which requires the notion of pinning.

Unreal packs its own garbage collection. This is a pattern you see quite often, GC is discarded because it's slow/the specific implementations don't fit the task, so an alternative GC is written to be used in a lower level language that doesn't require it natively. Contrast to Unity which uses C#. As for Minecraft, like I said originally you don't want to look at just GC for performance problems - that's a naive understanding of why languages perform poorly. Java is actually extremely fast and used in environments with tighter constraints than a game like MC.

https://github.com/gostor/awesome-go-storage#database

https://java-source.net/open-source/database-engines

Not a database but honorable mention, LMAX disrupter: https://lmax-exchange.github.io/disruptor/