Uptime & SLA

Uptime measures the actual availability of a service over a period. Common thresholds: 99 % (87.6 h downtime/year — hobby-acceptable), 99.9 % (8.76 h/year — typical shared hosting SLA), 99.95 % (4.38 h/year — premium managed), 99.99 % (52 min/year — enterprise multi-AZ), 99.999 % (5.26 min/year — telecom class). A Service Level Agreement (SLA) contractually commits the provider to a threshold and defines credit tiers if missed (e.g. 10 % monthly credit for missing 99.9 %, 25 % for <99 %). Watch out: SLAs usually only cover unplanned downtime, exclude maintenance windows and force majeure, and must actively be claimed. Verify real availability through external monitoring services (UptimeRobot, Statusgator) — not the provider's own status page.