Good to know, so more like a crontab entry for the database.

Where's the actual queue though? zmq isn't a message queue, it's more akin to a protocol. e.g. if I have N workers and M jobs, and M>N, where are all the >N indexed jobs kept while the others are being processed?

Like it appears you're using PUSH/PULL pattern, which means the jobs queue up in the publisher's memory (on a per PULL-peer basis..). So if the publisher crashes, those jobs are lost. If the number of jobs queued exceeds the high-water mark, those additional pushes are either going to discard messages or block. If it blocks, it looks like your code is going to have lots of other issues... If the worker crashes, I believe that queue is also going to be lost.