Engineering blog

Celery + Redis in production

War stories, debugging guides, and config lessons from teams running async task queues at scale.

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Your Celery queue depth alert is lying to you

Depth tells you how many tasks are waiting. It can't tell you the only thing that matters: how long. Alert on age, not count.

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Depth tells you how many tasks are waiting. It can't tell you the only thing that matters: how long. Alert on age, not count.

Dashboards are forensics, not defense. For silent async failures, the only number worth optimizing is how fast something interrupts you.

Flower shows all workers online. Tasks aren't being processed. Here's what's actually happening; and how to catch it before your users do.