not distributed systems, but I have a build your own KV store project. It is in TDD fashion with the tests. So, you start with simple functions, pass the tests, and the difficulty level goes up. When all the tests pass, you will have written a persistent key-value store.

https://github.com/avinassh/py-caskdb

I don't get how this is comparable to FoundationDB or DenoKV

Does one get updates for lifetime on Mac version?

Learning and Reviewing System Internals: Tactics and Psychology

I have noted your feedback and I do acknowledge that documentation on virtual WAL trait can be improved.