Fundamentals
Error Budget
The allowed failure remaining under an SLO. A 99.9% target permits ~43 minutes of failure a month.
Why interviewers ask about it
Frames reliability as a resource to spend. Under budget, ship faster; over budget, freeze features. It converts a values argument into a measurement.
Related terms
This term is part of the free System Design interview preparation module - browse the full glossary for every definition.