As data stores go go this is basically in memory only. The save and load process is manually triggered by the user and the save process isn't crash safe nor does it do any integrity checks.

I also don't think it has any indexes either? So search performance is a function of the number of entries.

In the world of Kubernetes and languages where a one-liner brings in a graph of 1700 dependencies, and oceans of Yaml, it's suddently important for a C thing to be one file rather than two.

Useful for embedded devices? Crashes, disk updates not important for ephemeral process?

Header-only C libraries are such an underappreciated pattern for embedding into larger projects. For vector search specifically, having something you can just drop into an existing C/C++ codebase without pulling in a whole database dependency is really appealing. Curious about the indexing strategy — is it brute force or does it support approximate nearest neighbor?

Would it work to replace the memory store with mmap?

Why to call it a header? Could be just a source file. Including sources is uncommon, but why not? Solid "amalgamation" builds are a thing too.