We use pgmq with the pgmq-go client, and it has clients in many different languages, it's amazing.
The queues persist on disk and visualizations of queues can easily be made with grafana or just pure sql requests.
The fact that the queues lives in the same database as all the other data is also a huge benefit if the 5-15ms time penalty is not an issue.
Same. Not that it means much, but I've been seeing 51820 being used in all documentation, blog posts, etc. Probably just copypasting the original examples, e.g.
Free is a term used by the community for decades, literally in the name of the Free Software Foundation. I guess you could argue that their need to explain what free means indicates it was a bad choice to use, but it is pretty standard now.