CORE METRICS
System Uptime
The percentage of time that a system is fully operational and available to users.
By Niketa Sharma, Founder at Runframe·Last updated Mar 2026
Uptime % = (Total Time - Downtime) / Total Time × 100
The percentage of time that a system is fully operational and available to users.
The Nines
- 99% (2 Nines): Down 3.65 days/year. (Okay for blogs).
- 99.9% (3 Nines): Down 8.76 hours/year. (Standard for SaaS).
- 99.99% (4 Nines): Down 52 minutes/year. (Enterprise grade).
- 99.999% (5 Nines): Down 5 minutes/year. (Telco/Critical Infrastructure).
Each additional "nine" is 10x harder to achieve. The cost of going from 99.9% to 99.99% is often not worth it for most applications.
ExSaaS Platform Availability Journey
“B2B SaaS improved from 99.8% to 99.95% uptime over 12 months. Key changes: Implemented database failover, added caching layer, and improved deployment process. Customer churn dropped from 12% to 6%.”
Impact
Doubled ARR growth through improved trust and retention
Resolution
Multi-region architecture with automated failover
Why Uptime Matters
The primary measure of reliability.
Often expressed in "Nines" (e.g., 99.9%).
Common Pitfalls
Chasing 5 nines (99.999%) prematurely
Focus on 3-4 nines first. The cost of 5 nines is rarely justified for non-critical systems.
Measuring uptime only at the server level
Measure from the user's perspective. Use synthetic monitoring to test actual user flows, not just server pings.