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Performance Optimisation and Core Web Vitals for Modern Web Platforms

The usual sign is a site that feels slower after changes, harder to ship, or too expensive to keep tuning one regression at a time.

Performance work for modern front ends where page loads feel slow, Core Web Vitals are slipping, or scripting cost is hurting key user journeys.

Short Answer

The site may still work, but key pages feel slower, less stable, or harder to explain than they should. LCP, INP, and CLS problems usually come from rendering, images, scripts, fonts, data loading, layout behaviour, or third‑party code. What matters is connecting the metric to a real route, journey, or release change, then improving performance in a way the product and team can keep.

Why It Matters

For product and commercial teams, the value is less friction: I trace slow routes, heavy scripts, and unstable templates back to the choices affecting conversion, trust, and release confidence.

Where This Fits

  • Core Web Vitals diagnostics across release, redesign, and migration work.
  • JavaScript, image, and caching changes that improve real user performance.
  • Performance reviews for live Next.js and modern front‑end stacks.

What I Look at First

I usually start by checking the affected templates, Core Web Vitals data, rendering path, image and font behaviour, third‑party scripts, caching, data loading, deployment history, and whether the issue is reproducible in production.

Common Engagements

  • Short regression investigations after a launch or release.
  • Performance audits that turn LCP, INP, CLS, and script cost into an ordered fix list.
  • Hands‑on remediation for the fixes most likely to move field data.

What Usually Changes

  1. Routes, templates, assets, scripts, and rendering paths that create regressions are isolated.

  2. Lab scores, field data, and local reproduction evidence are separated so the team can focus on real bottlenecks.

  3. Fixes are prioritised by user impact, commercial exposure, and engineering complexity.

  4. The team has a defensible plan for images, scripts, caching, rendering, and release verification.

  5. Release confidence improves without chasing arbitrary performance scores.

How This Usually Works

  1. Technical Diagnostic

    A focused review of affected routes, templates, deployment behaviour, crawl signals, CMS behaviour, performance bottlenecks, or code paths, followed by a prioritised fix plan the team can take into delivery.

  2. Recovery Sprint

    A short, concentrated engagement for a defined technical SEO, performance, CMS, Vercel, migration, or production issue where the business needs the cause isolated and the first fixes moved quickly.

  3. Embedded Delivery Support

    Senior hands‑on support inside an existing team where architecture, implementation, review, and delivery judgement all matter, especially when the work cannot be handed over as isolated tickets.

This May Not Be the Right Fit If

  • You only need a one‑off Lighthouse report and do not yet have room to change code, content, scripts, images, or release behaviour. If a real regression needs diagnosis, Next.js Core Web Vitals Regression Fix is the better starting point.
  • The team needs cosmetic speed advice rather than diagnosis tied to field data, templates, and user journeys. If the pressure is mainly third‑party scripts, Third‑Party Script Performance Optimisation is the more focused route.

Get in touch about the performance issue

A short description of the affected route, metric, or recent release is enough. I'll read it and suggest the next step.

Get in touch

Related Project Work

  1. Screenshot of the Nando’s website; part of John Kavanagh's development portfolio.

    A Complete Migration and Replatform for Nando’s

    On Nando’s restaurant pages, speed, structured data, and local discovery were handled as one customer path rather than separate score‑chasing exercises.

    View project
  2. Screenshot of the John Lewis website; part of John Kavanagh's development portfolio.

    The Optimisation and Rebrand of johnlewis.com

    On John Lewis, Core Web Vitals and front‑end optimisation work on high‑traffic retail pages left little room for regressions in speed, stability, or search visibility.

    View project
  3. Screenshot of the Selfridges website; part of John Kavanagh's development portfolio.

    A New User Experience and Features for Selfridges

    At Selfridges, e‑commerce front‑end work had to keep perceived speed, release quality, and commercial flows stable under pressure.

    View project

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