None if possible. In the safety critical parts you want to use software that - don't do dynamic any memory allocation, has bounded memory usage, never runs out

None if possible. In the safety critical parts you want to use software that - don't do dynamic any memory allocation, has bounded memory usage, never runs out of memory. - has bounded execution times - has low interrupt latency - can do checksum on data and internal state an option. (if need to load into memory) - is tested using the most rigorous standards, 100% verification and code coverage. If you write great relatively general but customizable database system like this with good indexing, you need only 5-10 customers and you are set. Safety-critical systems are growing in size and there is real need for software that can get easily certified. SQLite could probably get certified as a part a system at least as read only database. It's relatively solid code. But it will cost big money and I don't think anyone has done it.