So I have been working on this database or I guess more like a dbms, but need to find a way to have more reliable data. So the database works great but has issues if there is an error during read/writes.

Lets say someone shuts down the computer during a write. Well currently I have only once source of truth for that information. If it's not JSON readable then the data is lost. I know the strategies and I have read about ACID methods. What I am asking is for someone with experience to shed some light on how they did it. Did you create external copies in separate directories with some kind of logging system? What is the best way to go about this?