Meaning
The proportion or percentage of time that a computer system or digital service has been operational, healthy, and accessible.
Three examples from work
SLA review
DevOpsOur production API achieved 99.98% uptime this past quarter.
PMThat comfortably satisfies our enterprise customer SLA commitments.
Marketing claims
Sales RepCan we promise 99.99% uptime in our new enterprise sales contracts?
ArchitectOnly if we deploy multi-region database redundancy first.
Monitoring dashboard
LeadThe synthetic monitoring bot pings our health check endpoint every sixty seconds to record uptime.
DevAny dropped ping triggers an immediate alert to the on-call engineer.
Engineers refer to availability in 'nines' (e.g., 'three nines' = 99.9%, 'four nines' = 99.99%). Four nines permits only 52 minutes of downtime per year.