I know that the spirit of HN will strike me down for this, but sqlite is not a "sophisticated system". It assumes the hardware is lawful neutral. Real hardware is chaotic. Sqlite has a good reputation because it is very easy to use. In fact this is the same reason programmers like mmap: it is a hell of a shortcut.
I think the main thing is whether mmap will make sqlite lose data or otherwise corrupt already committed data
... it will if two programs open the same sqlite, one with mmap, and another without https://www.sqlite.org/mmap.html - at least "in some operating systems" (no mention of which ones)
> The operating system must have a unified buffer cache in order for the memory-mapped I/O extension to work correctly, especially in situations where two processes are accessing the same database file and one process is using memory-mapped I/O while the other is not. Not all operating systems have a unified buffer cache. In some operating systems that claim to have a unified buffer cache, the implementation is buggy and can lead to corrupt databases.
Sqlite is otherwise rock solid and won't lose data as easily
