Performance Doctor

Performance Doctor: practical plan

Performance diagnosis

Compare affected and healthy sessions

Segment by device, network, browser, region and cache state. Capture real-user LCP, INP and CLS alongside server TTFB. Verify whether “first-time” means cold cache or new account.

Inspect the critical path

Review document size, JavaScript bundles, render-blocking resources, image dimensions, font loading, third-party tags and API waterfall. Check CPU throttling and low-bandwidth behavior.

Backend checks

Compare API latency and payload size for new versus returning users. Look for extra onboarding calls, cache misses and expensive personalization.

Experiment safely

Optimize the largest measured bottleneck first. Test image formats, code splitting or deferred scripts independently. Do not remove accessibility or security behavior for speed.

Validation

Use representative devices and field data. Compare p75 metrics, conversion and error rates across a suitable window.

Release

Set performance budgets, add regression monitoring and keep rollback. Report the measured change, sample and limitations.

Measurement and review

Record the baseline, source, date range, denominator and owner. Use one primary measure plus quality guardrails; compare like-for-like cohorts and disclose missing data. Treat estimates as scenarios, not observed outcomes.

Risks and controls

Check relevance, consent, disclosure, workload and downside before scaling. Keep an evidence trail, obtain human review for material commitments, and pause if trust, quality or compliance signals deteriorate.

Next steps

1. Confirm the goal, audience and available capacity.
2. Gather the minimum evidence for a first test.
3. Assign an owner, budget and review date.
4. Run a small pilot, record outcomes and decide whether to iterate, expand or stop.