Since you mention no network endpoint, I assume it's on a single server. If so, have you considered SQLite? Assuming your cache is not massive, the file is likely to end up in Filesystem cache so most of reads will come from memory and writes on modern SSD will be fine as well.

It's easy to understand system with well battle tested library and getting rid of cache is easy, delete the file.

EDIT: I will say for most use cases, the database cache is probably plenty. Don't add power until you really need it.