SLOs vs SLAs: A Practical Guide for Small Engineering Teams
Your biggest customer emails asking for your uptime SLA. You say '99.9%'. You have no idea if you've been meeting it. You've never measured it.
Service Level Objectives and Agreements sound like enterprise bureaucracy, but a simple SLO practice helps small teams make better on-call decisions and build reliability with purpose.
SLA vs SLO vs SLI — the definitions that matter
SLI — A metric you measure. Uptime percentage. API p99 latency.
SLO — A target for an SLI. 'We aim for 99.9% uptime.' Internal commitments.
SLA — A contractual commitment to customers, usually with financial consequences for breach.
Calculating your error budget
An error budget is the amount of downtime your SLO permits.
For 99.9% monthly uptime: - Total minutes: 43,800 - Error budget: 43.8 minutes
If you've used 40 minutes this month, you have 3.8 minutes left. That changes how aggressively you deploy.
Setting your first SLOs
Start with what you already have data for. A team that has achieved 99.5% uptime historically shouldn't commit to 99.95%.
Practical starting SLOs: - API availability: 99.5% - Core feature availability: 99.0% - Background jobs: 95%
Using your status page as an SLO dashboard
AlertsDock status pages show 90-day uptime percentages per component. This is your de facto SLI measurement — use it as the source of truth when calculating whether you met your SLO.
When to invest in reliability vs features
Budget fully consumed → Freeze risky deploys. Focus on reliability.
Budget mostly intact → Normal velocity. Take reasonable risks.
Budget never consumed → You're over-investing in reliability. Redirect effort toward features.
Feature Guide
Uptime Monitoring
AlertsDock gives teams uptime monitoring for websites, APIs, TCP checks, DNS checks, SSL expiry, and fast alert routing without enterprise overhead.
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Compare AlertsDock with Better Stack for teams that want a more focused monitoring product covering uptime, cron jobs, status pages, and webhooks.
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