Measurement

Measurement interviews ensure performance work is provable. Combine synthetic lab checks, real-user monitoring, load tests for capacity, and skepticism about benchmarks that lie.

Subtopics: synthetic tests, real user monitoring, load testing, benchmark pitfalls.

On interviews: which metric proves a deploy helped users; when lab Lighthouse disagrees with CrUX; how to ramp load without coordinated omission; why p95 matters more than mean.

Common pitfalls: optimizing to a single synthetic score; load tests with unrealistic think time; ignoring geographic and device variance.

The trade-off is measurement fidelity versus cost, time, and environment complexity.

Checklist:

• Pair lab and field evidence.
• Use percentiles and budgets, not only averages.
• Model realistic traffic ramps.
• Document environment assumptions.