Feature request: in-memory storage

[susliko]

Having an option to use in-memory storage instead of MongoDB would make it simpler to use the Mockingbird in short-living test environments (e.g. in hermetic CI runs)

[danslapman]

Hi! This one is in mind for a while :) Hopefully, I'll start my work on it in Q1 2023.
While it's not a long-term solution, you can use FerretDB upon h2 DB if you need this feature right now.