Error Budgets
An error budget is the amount of unreliable service behavior allowed by a service level objective during a defined period. Teams use it to make shared, data-based decisions about release risk and reliability work.
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Intro
Error Budgets
An error budget turns a reliability target into room for imperfect service. It states how much user-impacting failure a team can tolerate during a defined period.
The core relationship is:
service level objective → allowed failure → measured consumption → agreed action
This relationship changes a vague argument about stability into a decision process. Product and engineering teams can move quickly while the service stays within its objective. When failures consume too much budget, the same teams shift effort toward reliability.
Start with the service level objective
A service level indicator, or SLI, measures service behavior that matters to users. A request success ratio is one example:
good requests / total eligible requests
A service level objective, or SLO, sets a target for that indicator over a time window. An availability SLO might require 99.9 percent of eligible requests to succeed during four weeks.
The error budget is the complement of the SLO:
error budget = 100 percent − SLO
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Sources
- https://sre.google/sre-book/service-level-objectives/
Supports
- Definitions and distinctions for SLI, SLO, and SLA
- User-centered indicator selection and limits of aggregate measurement
- SLO violation rate as an input to release decisions
- Quiz question 7 and the first reference-link rationale
- https://sre.google/sre-book/embracing-risk/
Supports
- Error budgets as objective measures of permitted unreliability
- Alignment of product velocity and reliability incentives
- Release continuation while budget remains and reliability action after exhaustion
- Quiz question 1 and the second reference-link rationale
- https://sre.google/workbook/implementing-slos/
Supports
- Good events divided by total events as an SLI pattern
- Error budget as one hundred percent minus the SLO
- Event-based budget calculation and incident budget consumption
- Rolling and calendar-aligned window tradeoffs
- Four-week rolling window, weekly summaries, and quarterly reports as a general starting approach
- Stakeholder agreement, policy contents, dashboards, reports, continuous review, and decision making
- Quiz questions 1, 6, 7, 9, and 10 and the third reference-link rationale
- https://sre.google/workbook/error-budget-policy/
Supports
- Policy goals, non-goals, change controls, reliability actions, exceptions, and escalation
- A 99.9 percent SLO producing a 0.1 percent budget and one thousand errors per million requests
- Policy as protection rather than punishment
- Quiz questions 2, 3, and 6 and the fourth reference-link rationale
- https://sre.google/workbook/alerting-on-slos/
Supports
- Burn-rate definition and interpretation
- Multiple burn rates for urgency-aware paging and ticketing
- Multiwindow alerting using long and short windows
- Low-traffic denominator problems
- Quiz questions 4, 5, 8, and 10 and the fifth reference-link rationale
- https://github.com/sindresorhus/awesome
Supports
- Discovery of the Awesome Site Reliability Engineering list
- https://github.com/dastergon/awesome-sre
Supports
- Discovery of the Awesome SRE Tools list
- SRE ecosystem relevance of SLO monitoring and alerting resources
- https://github.com/SquadcastHub/awesome-sre-tools
Supports
- Discovery of Prometheus, Grafana, and SLO Exporter as SRE ecosystem tools
- https://prometheus.io/docs/introduction/overview/
Supports
- Prometheus time-series collection, querying, recording rules, and alerting
- Prometheus Awesome Links rationale
- https://grafana.com/docs/grafana/latest/
Supports
- Grafana dashboards, data-source queries, transformations, annotations, and alerting
- Grafana Awesome Links rationale
- https://github.com/seznam/slo-exporter
Supports
- Event processing into standardized SLI and SLO metrics
- Included examples, Grafana dashboards, Prometheus recording rules, and alerts
- SLO Exporter Awesome Links rationale