I suppose PubSub is at least slightly better than this because it's not a perfect queue. I.E. messages that are not acknowledged will be retried with exponentia

I suppose PubSub is at least slightly better than this because it's not a perfect queue. I.E. messages that are not acknowledged will be retried with exponential backoff. That at least gives some time to process some stuff before you encounter the poison message again. Whereas with a FIFO queue you're completely screwed.