After an outage, a queue holds 1.8 million messages. Consumers process 2,000 a second, while producers keep adding 1,500 a second. How long until the backlog is gone?

Answer

About 60 minutes. In review, anything from 40 to 90 counts as right.

The worked estimate

The backlog shrinks by 2,000 − 1,500 = 500 messages a second. 1,800,000 ÷ 500 = 3,600 s = 60 minutes. Only the spare capacity drains a backlog, so adding consumers for the recovery shortens it a lot.

Numbers: Numbers to know.

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