An error budget turns reliability into a currency: spend it on shipping fast, or protect it when it runs low.
An error budget is the amount of unreliability a service is allowed, calculated as one minus the SLO. If the SLO is 99.9%, the error budget is 0.1%, the failures you can absorb in the window before you have breached the target.
If your SLO is 99.9% over 30 days, you are permitted 0.1% failures in that window, that is your budget. Every incident spends some of it. As long as budget remains, you can take risks and ship quickly; when it is nearly exhausted, the sensible response is to slow down and prioritise reliability work.
The error budget resolves the perennial tension between shipping features and staying reliable by making it a shared, quantified rule rather than an argument. It gives development and operations the same scoreboard: healthy budget means go faster, depleted budget means stabilise.
Sentinel AI can weigh incidents by how fast they are burning an error budget, focusing autonomous resolution where reliability is most at risk.
As one minus the SLO. A 99.9% SLO gives a 0.1% error budget over the SLO window.
Teams typically freeze risky changes and prioritise reliability work until the budget recovers, which is the point of having one.
Ops Singularity turns open telemetry into autonomous, governed resolution. See it on your own stack.