Backend & systems·Queues, streams and delivery semantics
the producers are writing faster than the consumers are reading and the backlog has been growing all afternoon.
Consumer lag
Also calledqueue depth, backlog
How far behind the head of the stream a consumer group is, or how many messages are waiting in a queue. It is the single best health metric for an async system, because it captures capacity, failure and slowdown in one number. Alert on the trend rather than the absolute value: a constant lag is a working system, a rising one is an outage in about an hour.