Cassandra is a constant struggle with the GC. I’d guess the cost of running it is at least an order of magnitude greater compared to if it had been implemented in c++ or something more sensible.
In my opinion it's a colossal waste of resources. Classic example of using the wrong tool for the job.
If you were starting a database-focused company from the beginning than choosing C++ is a better decision, which is exactly what ScyllaDB has done with their cassandra clone. Along with general algorithm and decision improvements, it'll provide 10-100x the same performance at lower latency on the same server.
We're also starting to see more projects written in Go now, which is still a managed runtime but usually better at handling these kinds of low-level systems.
.NET Core on Linux is very fast and there are some great developments around fast low-level (yet managed) managed memory manipulation that can lead to some very fast software.
Something like Java makes implementation easier, but operation more difficult and costly.
