Sure, you can glue things together with lua. Here is a script that handles descheduling from a sorted set: https://github.com/sorentwo/kiq/blob/master/priv/scripts/des...

That definitely does the job. My point is that it is much more complex than a select/update clause in SQL.

Yep, TaskTiger also uses Lua quite extensively ([0]) to ensure atomicity when moving tasks between various stages of processing (queued, active, scheduled, errored).

[0] https://github.com/closeio/tasktiger/blob/master/tasktiger/r...