Partial Outage

Definition

A partial outage is a failure window in which a service is unavailable or degraded for a subset of its surface: one region, one API route, one model tier, one auth path, one traffic class - while the rest functions normally. “Up” and “down” are both false descriptions of it.

The problem

Binary status vocabulary forces partial outages into the wrong bucket. A vendor reporting “no incidents” can be simultaneously true (no global outage) and useless (your route is timing out).

Why it matters

Partial outages are the most common failure mode of large platforms, they break failover logic that assumes whole-system down, and they are the hardest windows to evidence afterwards because every aggregate smooths them away.

Practical example

One region of a provider returning 5xx while two others serve normally; completions fast while realtime routes hang; public API degraded while the consumer app is untouched. Each is invisible to any single number - and to any observation from one vantage point.

How RELIASTRA approaches it

Per-observation storage with an explicit error type is what makes the shape of a partial outage visible: RELIASTRA reports the exact endpoint and window it observed failing, and prints “insufficient data” wherever a record from one observation point cannot speak to the rest of the surface.