you can certainly encode queue in many ways. mkfifo just work. But integrating the queue in the DB isn't a bad idea if you want to have both the queue and the db in a shared state.

I am happy that my queue inherit ACID properties.

SQLite simply doesn't allow concurrent write so it is a no go for a queue.

I don't know much about SQL Server and MySQL but I wouldn't favor a lockin closed source software or anything remotely connected to Oracle.

At the end, only Postgresql remains I guess. Also, Postgresql is super solid and the closest to SQL standard.

> Plain old files on the file system

…and accessed over SFTP.

I worked for a company in the health industry and one of the labs we integrated refused to call a HTTPS endpoint whenever a result was ready, so we had to poll every _n_ mins to fetch results. That worked well until covid happened and there were so many test results causing all sorts of issues like reading empty files (because they were about to be written to disk) and things of that nature.

std::queue and a big swap file

Don't forget the plain old postit notes.