They poll. It's easy however to add pub/sub via redis. Queues are categorized in frequency. So for example a notification queue might process every minute or 5 minutes, a reconciliation queue might run every 12 hours, or have a fixed time, like daily at 2am and 6pm, etc. Each queue runs on its own goroutine on its onwn schedule, and every worker runs all queues. I can also adjust how many items a worker can pull each time so queues do not get backed up. Say there is some criteria an account needs to meet to be eligible for some feature. If that criteria requires some expensive db queries, I can run a daily job that pulls 100 accounts each time to check that they meet the criteria. But if the instances can process more, I can configure it to pull 1000 accounts. Or I can add 9 workers and each pulls 100 accounts.

Usually what I do is pull the records that were updated least recently (as in they should be ahead of the queue). So if a previous worker locked the oldest X records, the second worker will pull the next batch bc the condition will exclude the previously updated (locked) records. There's a lot of flexibility you can add with just these controls: schedule, frequency, batch size, number of workers.