One edge case is when the code processing the message has not finished, but the invisibility window lapses, and another copy of the same message gets dequeued. At this point, there are two active copies of that message being processed.

server push; a push technology

[…]behind them a granola-looking mom in denim overalls and a t-shirt was pulling in to do her drop-off . . . from a Prius.

The deltidiodont morphology did not survive the end-Permian extinctions; the modern articulated brachiopod fauna is dominated by cyrtomatodonts with crurae and loops.