The scenario you've lived It's 2am. Someone pings you: emails aren't going out. You check Flower. Every worker is green; online, healthy. Queue depth is climbing. Nothing is moving. This is a ghost worker : a process that's alive, but not consuming. What actually happens When a Celery worker reconnects to Redis after a network hiccup, it can end up in a broken state where: It maintains its heartbeat (so Flower shows it as online) It holds its prefetched tasks (so t...