Putting thought into design patterns and a storage engine that accents that choice, it's sometimes possible to eschew caching and distributed storage altogether - saving you from a whole host of complexity.

It can also be challenging to accurately assess a database's performance and correctness. I've been using C/Rust bindings when possible for the former, and Aphyr's Jepsen test results for the latter. Unfortunately there's no silver bullet on these topics - you pretty much have to test all your use cases.