Any idea if there's a database layer (eg SQLite, PG, etc) on the systems?
- 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.
You can think as each string being “functional“: given the same set of inputs you expect the same set of outputs.
"Real men don’t use backups, they post their stuff on a public ftp server and let the rest of the world make copies."
Real programmers don't use persistent storage, they just rely on physical reality in general.