Jonas Adler
TIL: Why My Prometheus Histogram Was Lying
A short note on bucket boundaries, aggregation, and the misleading percentile that started the investigation.
Context
A short note on bucket boundaries, aggregation, and the misleading percentile that started the investigation. This sample entry outlines the context, the trade-offs, and the operational result in a form that can be expanded into a complete technical piece.
Approach
The work begins with a clear constraint: make the next decision observable, reversible, and easy for another engineer to understand. The details here are intentionally representative rather than production-specific.
What changed
The key lesson is to reduce uncertainty early. Define a measurable baseline, change one variable at a time, and record the evidence before scaling the approach.
What happens when you rush to the conclusion
Document the assumptions, define an observable success signal, and keep the change reversible until the evidence supports a broader rollout.
The writers who stay in the uncertainty
Every implementation has a cost. The useful question is which cost the team can understand, monitor, and accept before the system is under pressure.
Good infrastructure makes the safe path the easy path.
What this requires of the reader
The result is a smaller surface area for surprise: clearer ownership, fewer manual steps, and an operational path that can be rehearsed before it is needed.
Why it is worth cultivating
Keep the measurement, the decision record, and the rollback plan close to the implementation. They are part of the system, not an appendix.
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About the author
Shirasaka Ren
I keep other people’s infrastructure alive for a living, and I would very much like to tell you about it