Uptime
Five Nines
99.999% uptime
Five nines of availability means 99.999% uptime — a service level that allows no more than 5 minutes 15 seconds of downtime per year. It is the gold standard for telecom and critical infrastructure but is rarely achievable, or economically justified, for typical web SaaS.
In depth
Each additional nine reduces allowed downtime by a factor of ten. 99% (two nines) allows 3.65 days of downtime per year, 99.9% (three nines) allows 8.77 hours, 99.99% (four nines) allows 52.6 minutes, and 99.999% (five nines) allows just 5.26 minutes.
Reaching five nines requires multi-region failover, automated incident response, redundant networking, and zero single points of failure. It is expensive — usually 10x to 100x the cost of running at 99.9% — and rarely justified outside of payments, telecom, and life-critical systems.
Why it matters
Most SaaS contracts specify three nines or four nines. Knowing what nines you actually need stops you from over-engineering — and lets you call out vendor SLAs that quietly only commit to 99% (3.65 days a year of permitted outage).
How Lemwatch helps with five nines
Lemwatch monitors five nines continuously and alerts you the moment something changes.
Public status pages →Related terms
Uptime
Uptime is the percentage of time a website or service is reachable and serving correct responses. It is the he…
SLA
A service level agreement (SLA) is a contractual commitment between a provider and a customer specifying a mea…
Downtime
Downtime is any period in which a website or service is unreachable, returns errors, or fails to meet its agre…
MTTR
Mean Time To Recovery (MTTR) measures the average time it takes to restore service after an incident begins. I…
Incident
An incident is a confirmed period of degraded or unavailable service that requires human attention. Incidents …
Browse the full Lemwatch monitoring glossary (47 terms).