Use Cases
An SLO is only useful if a breach points somewhere. This one goes from a threshold crossing to the commit that caused it in three surfaces, without leaving the same time range.
signal checkout p99 380 ms · threshold 200 ms
The path
One SLO holds the whole path together: checkout p99 at or under 200 ms. Every surface below is filtered to the window where it stopped being true.
The rule is written against the SLO, so the notification carries the threshold, the observed value and the evaluation window. 380 ms against 200 ms, sustained across three windows.

p50 has not moved. p99 has. That shape means a slow tail on one route rather than a service-wide slowdown, and the route breakdown names it: POST /checkout.

Split the same endpoint by service.version and the step change has an owner: p99 120 ms on abc123, 380 ms on def456. The traces under def456 carry 50 db.query spans where the earlier ones carry 3.

outcome
Reverted def456 at T+9:20. p99 back under the threshold on the next evaluation window.
What it does
One endpoint, one key. Traces, logs, metrics and sessions land on the same trace id from the first request.