Error budget

An error budget is the amount of failure a service is allowed in a time window before it breaks its service level objective (SLO). It equals 100% minus the SLO. Teams spend the budget on releases, experiments and incidents. When the budget runs out, the team shifts effort from new features to reliability work.

How to calculate it

Multiply the window by 1 minus the SLO. Over 30 days (43,200 minutes):

99.9% allows 43.2 minutes of downtime.
99.95% allows 21.6 minutes.
99.99% allows 4.32 minutes.

Burn rate is how fast you spend the budget. It is the observed error rate divided by the allowed error rate. A burn rate of 1 uses the budget exactly over the window. A burn rate of 14.4 sustained for one hour uses 2% of a 30-day budget, which is a common threshold for a fast-burn page.

Why it matters in production

An error budget gives product and engineering one shared rule for release speed. It replaces arguments about risk with a number, and burn rate alerts catch fast outages and slow leaks without paging on every blip.