Short answer
Commission a baseline and prioritized fix list before a full rebuild. Ask which routes and actions are slow, what evidence supports the diagnosis, and how the same experience will be measured after changes. Bundle size, a lab score and real user performance describe different things.
Describe where users experience the delay
Provide representative URLs and actions: opening a service page, filtering a dashboard, starting playback or submitting a form. Record device and network conditions where the issue appears. A heavy landing image and a slow dashboard interaction need different investigations.
Distinguish lab tests from field data. Google’s Core Web Vitals describe loading, interaction responsiveness and layout stability through LCP, INP and CLS. A repeatable lab test helps diagnose problems; real-user measurements describe actual visitors. If field data is unavailable, label the gap instead of claiming a pass.
Use project results as context
My Sound Of Meme case study describes React bundle optimization using lazy loading, route-level code splitting, shared components and rendering optimization. The approximately 8 MB to 2 MB figure is a historical project estimate without published build artifacts or test conditions, not a reproducible benchmark or a promised result for another site.
Agree exactly what is measured: build output, route JavaScript, compressed transfer size or a user-facing metric. Compare like for like. A smaller bundle can help, but does not by itself establish faster server responses, improved conversion or higher rankings.
Request a fix list with tradeoffs
Each proposed change should address an observed issue. Possible findings include oversized images, JavaScript shipped to routes that do not need it, expensive rendering, third-party scripts or slow data fetching. Separate quick changes from architecture work and explain what might regress.
Lazy loading helps when code is not needed immediately, but deferring a critical interaction can move the wait to the moment of use. Agree which features can load later and check their loading and error states. A rewrite should follow evidence that the current structure prevents the necessary improvement.
Agree the before-and-after evidence
Use the same routes, conditions and actions in the final comparison. Keep the original measurements and record what changed. Check that forms, navigation and key application workflows still function after optimization.
Provide the repository access plan, hosting setup and business journey you care about. The performance package in the planner is a starting point; final scope follows the findings. Neither a perfect lab score nor a specific search position should be an assumption in a performance proposal.
Further reading
Common questions
Does a faster website automatically rank first?
No. Performance improves the experience, but visibility also depends on relevance, useful content and other factors. Agree on work and evidence, not a ranking position.
Do I need to rebuild React in Next.js?
Not automatically. Measure the routes and workflows that matter. The recommendation should explain why targeted fixes suffice or why an architectural change is needed.