The filesystem is very easy to use for simple things by comparison to a DB, and it's more accessible from the shell. But you're right, the filesystem is very difficult to use in a power failure safe way. SQLite3 has great power failure recovery testing, so the advice to use SQLite3 for any but the simplest things is pretty good.

It'd be very nice to get some sort of async filesystem write barrier API. Something like `int fbarrier(int fd)` such that all writes anywhere in the filesystem will be sync'ed later when you `fsync()` that fd.

It would also be very nice to have an async `sync()`/`fsync()`. That may sound oxymoronic, but it's not. An async `sync()`/`fsync()` would schedule and even start the sync and then provide a completion notice so the application can do other work while the sync happens in the background. One can do sync operations in worker threads and then report completion, but it'd be nice to have this be a first class operation. Really, every system call that does "I/O" or is or can be slow should be / have been designed to be async-capable.