Glossary / Cloud & infrastructure

Uptime & availability (the nines)

Uptime is the share of time a system is actually working, usually quoted in "nines": 99.9% allows about 43 minutes of downtime a month; 99.99% allows about 4. Every extra nine costs real engineering — redundancy, health checks, automatic failover. A serious provider writes its uptime target into an SLA with consequences, which is exactly what ours do.