If I understood correctly, the queue implementation in the blog post holds a transaction while an operation is in progress.

I see the advice to make it as short as possible, but why can’t we update the status column to, say, “processing” and avoid potentially long transactions at all?

This works well for jobs that are long-ish. You need another process to sweep for orphaned jobs and requeue or fail them. Add a timestamp of when it got picked up to keep track