serviceuptime

Service uptime is a measure of the availability and proper functioning of a service over time. It is commonly defined as the proportion of time during a reporting period when the service is accessible and performing its intended functions. Uptime is distinct from maintenance downtime, which is planned and scheduled.

Uptime is typically expressed as a percentage and is measured using monitoring tools that test availability (synthetic checks) and real user monitoring. Key metrics include uptime percentage, availability, MTBF (mean time between failures), MTTR (mean time to repair), and MTTF (mean time to failure). Uptime can be calculated as (total_time - downtime) / total_time × 100. Downtime includes periods when the service is unavailable or fails to meet defined service criteria.

Common uptime targets include 99.9%, 99.95%, 99.99%, and 99.999%. In a 8760-hour year, these correspond to about 8.76, 0.87, 52.6, and 5.26 minutes of downtime respectively. Agreements may specify service level objectives (SLOs) and service level agreements (SLAs) with penalties or credits if targets are not met. Uptime reporting should define what constitutes availability, geographic scope, and affected components.

Many factors affect uptime, including infrastructure reliability, network connectivity, software defects, maintenance windows, and external dependencies. Strategies to improve uptime include redundancy and failover, load balancing, graceful degradation, automated alerting and remediation, blue/green deployments, and robust incident response and disaster recovery plans.

Uptime data informs contracts (SLA), operational reliability (SLO/SLI), and customer trust. It is increasingly collected with both synthetic checks and real-user monitoring to provide a comprehensive view of availability across all service components and regions.