⏱️Uptime

NEW

The proportion of time a system or service remains operational and accessible to users.

DESCRIPTION

Uptime measures service reliability and is often expressed as an SLA percentage (e.g., 99.9%). It guides operational goals and error budgets in SRE practices. Uptime depends on redundancy, monitoring, incident response, and resilient architecture. Organizations track uptime with health checks, metrics, and alerting. High uptime reduces business disruption but requires investment in reliability engineering.

ALTERNATIVE DEFINITIONS

Wikipedia

Uptime is a measure of system reliability, expressed as the percentage of time a machine or system has been working and available.

Defines uptime as a reliability measure with percentage expression.

Source

Cloudflare

Uptime is the amount of time a website or service is available to users.

Focuses on user-perceived availability for web services.

Source

Microsoft Azure

Monthly Uptime Percentage is calculated using total minutes in a month minus downtime over total minutes in a month.

Provides a formal SLA calculation for uptime percentage.

Source

RELATED TERMS

Availability SLA Reliability Mean Time Between Failures Mean Time To Recovery Service Level Objective SLA Uptime Percentage

COMPETING TERMS

Downtime

KNOWLEDGE AREAS

Observability & Telemetry Cloud Infrastructure Data Services

TARGET AUDIENCE

DevOps Engineer Cloud Architect IT Manager Chief Technology Officer Security Architect

EXTERNAL SOURCES

• Wikipedia - Uptime
• Google SRE Book - SLOs and error budgets relating to uptime
• AWS Well-Architected - Reliability pillar guidance for uptime
• Prometheus - Monitoring fundamentals to measure uptime

TOP QUESTIONS

What does 99.9% Uptime mean?

It allows roughly 8.76 hours of downtime per year, setting expectations for service reliability and error budgets.

Category: Metrics

How is Uptime measured in practice?

Health checks, synthetic probes, real-user monitoring, and SLA calculations track availability over time.

Category: Observability

What factors most impact Uptime?

Redundancy, fault isolation, failover, robust monitoring, and fast incident response are key contributors.

Category: Requirements

How do SLOs relate to Uptime?

SLOs define target availability; error budgets formalize acceptable downtime to balance innovation and reliability.

Category: Management

What’s a common misunderstanding about Uptime?

High uptime does not guarantee good performance; latency and correctness also matter.

Category: Misunderstanding

What are typical Uptime SLAs for cloud services?

Common tiers are 99.9%, 99.95%, and 99.99%, depending on product and region.

Category: Overview

How to improve Uptime cost-effectively?

Introduce redundancy for critical components, use auto-recovery, and prioritize rapid MTTR.

Category: Best practices

What is the risk of chasing 100% Uptime?

Costs rise sharply; trade-offs with agility and complexity can harm overall reliability.

Category: Risk

How should Uptime be reported to stakeholders?

Use clear SLAs, SLO dashboards, and incident postmortems that contextualize availability figures.

Category: Collaboration