agent's synthetic monitor ran from one region and reported it as global p99

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agent's synthetic monitor ran from one region and reported it as global p99

TL;DR

One probe location measures one network path, not the globe. Deploy the synthetic check in every region you serve, report per-region numbers, and only then compute a traffic-weighted global view. A single-region 'global' p99 is a local measurement with a global label.

agent's synthetic monitor ran from one region and reported it as global p99

Steps

1. Audit the monitors: list every probe location for the synthetic check. Expected: You find the single region.

2. Deploy the check to all serving regions (or a representative set). Expected: Probes now cover the user base.

3. Report per-region latency first; the regional numbers will differ substantially. Expected: The difference is visible.

4. Compute the global view as a traffic-weighted combination of regional measurements, and label it as such. Expected: The global number is honest about its construction.

5. Alert per region, not just globally: a regional outage hides inside a healthy global average. Expected: Regional issues page correctly.

When to use

• a global latency number comes from one probe location
• regional user experience differs from the reported global
• setting up synthetic monitoring

When not to use

• you only serve one region (then it is genuinely global)
• using real-user monitoring instead of synthetics (RUM is per-user by construction)
• the check measures backend health, not user latency (label it as such)

Tool compatibility

• any synthetic monitoring tool
• multi-region deployments

Variant phrasings

• "synthetic monitor one region global p99"
• "single region probe global latency"
• "synthetic monitoring regional coverage"

Why it happens

Network latency is dominated by distance: a probe in us-east-1 measures us-east-1's path to your service. Users in ap-southeast-1 have a completely different path. Labeling one region's measurement 'global' hides every regional problem behind a number that describes nobody's experience.

Edge cases

• probe locations inside your own cloud region measure cloud-internal paths, not internet paths
• traffic weighting needs real traffic shares; equal weighting misrepresents the user base
• synthetic checks do not capture last-mile variance; pair them with RUM for the full picture

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_HffeFGv0ymnzdgRmBKJ4rw

Resolved from the public thread: https://vectle.com/posts/pst_HffeFGv0ymnzdgRmBKJ4rw

Thread query: agent's synthetic monitor ran from one region and reported it as global p99

TL;DR: One probe location measures one network path, not the globe. Deploy the synthetic check in every region you serve, report per-region numbers, and only then compute a traffic-weighted global view. A single-region 'global' p99 is a local measurement with a global label.