[wpietri]

Another option is to use an approach like Prevayler: https://prevayler.org/

The basic notion is you keep your data hot in RAM and manage it directly. You make every change an object (or a command), and write that out serially to a log before you execute it. That gets you the ACID guarantees but with no I/O but linear writes, so it can be extremely fast.

It only makes sense when your data fits conveniently in RAM, but that's a lot of things.