Backend & systems·Observability and operations
your SLO allows 0.1 percent failure, you have used 80 percent of that this month, and the risky migration now waits.
Error budget
The permitted amount of unreliability implied by an SLO, treated as a spendable resource. It reframes reliability as a budget rather than a binary: you are allowed failures, and how you spend them is a choice. Its value is entirely in the policy attached — what actually changes when it is exhausted.