One location lies: why outage detection needs more than one region

A monitor that checks from a single location is answering a narrower question than you think. It isn’t telling you “the service is down.” It’s telling you “the service is unreachable from here, right now.” Those are very different claims — and conflating them is the root cause of both false alarms and missed outages.

The two ways a single vantage point fails

False positives. The internet between your one probe and your service is a chain of networks you don’t control. A peering dispute, a congested transit link, or a brief routing flap can make a perfectly healthy service look dead from one location. Your probe reports DOWN, someone gets paged at 3 a.m., and by the time they log in everything is green. Do this a few times and your team stops trusting the pager.

False negatives. The mirror image is worse. If your single probe happens to sit in the same region as your service, it can sail right through an outage that’s crushing users on another continent. The check is green, the dashboard is green, and support tickets are the first you hear of it.

What multiple regions actually buy you

Checking the same target from several regions turns one ambiguous signal into a pattern you can reason about:

• Down from one region, up from the rest → almost certainly a network path problem, not your service. Don’t page anyone.
• Down from every region at once → a real outage. Page immediately.
• Down from regions in one geography → a regional CDN, DNS, or routing issue affecting a specific set of users — often invisible from HQ.

The rule that falls out of this is simple: require agreement before alerting. Only open an incident when two or more regions independently confirm the failure. One region’s bad afternoon never reaches your team.

Confirmation without slowing down

The usual objection is that waiting for a second region delays the alert. In practice it’s a few extra seconds, and it’s paired with a second safeguard — a consecutive-failure threshold — so a single dropped packet on one check doesn’t count. Two regions, two checks: enough to kill noise, fast enough that a genuine outage still pages you well under a minute.

The bottom line

A single monitoring location can’t separate “your service is down” from “the network between us is down,” and it can be blind to outages happening somewhere else entirely. Multiple regions plus a confirm-before-alerting rule fix both problems at once — fewer false alarms, and the regional outages a single probe would miss. Measure your service the way your users reach it: from more than one place.

See how multi-region confirmation works. Explore ping monitoring →