Why queues don’t feel “instant” in real backend systems?

When I first learned about queues and background workers, I imagined something like this: request comes in job goes into queue worker picks it up immediately done In my head, everything was basically instant. But when you actually run a real system, it doesn’t behave like that. There is always a gap Between: pushing a job into the queue and a worker picking it up There’s always a small delay. Sometimes tiny. Sometimes noticeable. And that gap changes how the system feels . Why that matters That