Error Budget Calculator

Start with current performance. If you're at 99.95%, set SLO at 99.9% to have headroom. Don't aim higher than you can sustain. Set it based on user expectations, not arbitrary targets. A batch job may only need 99%, while a payment API needs 99.99%.

Define actions at thresholds: >50% remaining = ship freely, 20-50% = careful deploys, <20% = reliability focus only, 0% = freeze. Document it and get team buy-in before the first incident.

Some teams exclude planned maintenance from error budget. Others include it to incentivize zero-downtime deploys. Google's SRE book recommends including planned downtime — it forces you to build rolling updates and blue-green deploys.

When you're spending too much engineering time on reliability for diminishing returns. Balance reliability investment vs feature velocity. If you're hitting 99.99% SLO but users only expect 99.9%, you may be over-investing in reliability.

High burn rate = more incidents = more on-call load. Error budgets help justify investing in reliability to reduce on-call burden. If you're constantly exhausting budget, use it as evidence to leadership that toil reduction work is critical.

Track failed requests / total requests (request-based) or downtime minutes / total minutes (time-based) over a rolling window. Use metrics from your APM, load balancer logs, or synthetic monitoring to calculate current error rate.

Prometheus with recording rules, Datadog SLO monitors, Google Cloud SLO monitoring, or custom dashboards. Many teams build Grafana dashboards with error budget burn rate panels and alerts. Warden can track uptime-based SLOs automatically.

Request-based is more precise for APIs and services with variable traffic. Time-based is simpler for availability monitoring and lower-traffic services. Use what matches your SLI. If you measure success rate, use request-based. If you measure uptime, use time-based.

Use multi-window, multi-burn-rate alerts. Alert if 1-hour burn rate > 14.4x (fast burn) OR 6-hour burn rate > 6x (slow burn). This catches both sudden spikes and gradual degradation. Google's SRE Workbook has detailed alert thresholds.

Warden tracks your uptime SLI automatically with 30-second checks and can alert when your error budget consumption exceeds thresholds. It calculates burn rate in real-time so you know immediately when you're at risk of exhausting your budget.