Featured case study
Selfridges
Lead front‑end developer within Selfridges' e‑commerce Customer Experience team, delivering new features, considerable refactoring, and platform performance improvements.
Technical Lead & Senior Software Engineer
Hands‑on engineering leadership for complex digital transformation programmes. I help product and engineering teams turn fragile legacy web estates into robust platforms that are faster and easier to maintain, scale, govern, and improve.
I'm John Kavanagh, an award‑winning software engineering specialist based in sunny cloudy Brighton, UK.
I am an enthusiastic senior software engineer and technical leader with over twenty‑three years of hands‑on experience.
I help teams and clients design, build and improve websites, applications and web platforms, pairing architecture, delivery judgement and hands‑on TypeScript, React, HTML, and CSS.
My portfolio is diverse; I work with global clients, solving real-world problems, including:
- engaging businesses, politicians, academics, and world leaders to shape global agendas;
- helping a major browser vendor explore AI‑driven tools for clearer, more useful browsing experiences;
- helping prospective car buyers find just the right configuration for their next sports car;
- ... and creating a digital home and web shop for a fledgling Sussex vineyard.
Featured Case Studies
- Featured case study
Virgin Atlantic
& HolidaysLead engineer on Virgin Atlantic & Holidays' large‑scale replatforming programme, unifying twelve disparate applications within a new headless architecture built with React and Next.js.
- Featured case study
Microsoft Edge
DevToolsPrincipal engineer leading AI‑driven browser tooling within Microsoft Edge DevTools, including real‑time content simplification, integrated issue reporting, and developer feedback pipelines.
How I Usually Help
Embedded Technical Leadership
Principal‑level support inside active delivery when architecture, standards, mentoring, documentation, ownership transfer, and implementation decisions need strengthening whilst the team keeps shipping.
Fractional Technical Leadership
Senior technical direction for organisations that need CTO‑style judgement across roadmap, suppliers, architecture, and release risk before a permanent leadership hire makes sense.
Next.js Platform Architecture
Define Next.js platform boundaries when domains, routes, tenants, brands, content ownership, data ownership, deployment models, or team responsibilities are making change unsafe.
Headless Architecture Consulting
Headless architecture advice before CMS, content model, preview, revalidation, metadata, schema, media, localisation, and editorial ownership decisions become expensive to reverse.
Next.js Platform Consulting
Senior platform assessment and technical direction for React and Next.js estates where routing, CMS, deployment, SEO, ownership, and delivery risk have become one problem.
Performance Optimisation and Core Web Vitals
Route‑level performance work for modern front ends where field data, Core Web Vitals, scripts, fonts, images, data loading, or templates are weakening important user journeys.
Previous Clients
John Lewis logo 
The BBC logo 
GOV.UK logo 
HSBC logo 
British Airways logo 
eBay logo 
Condé Nast Britain logo 
Nintendo logo 
Lotus Cars logo 
Team GB logo 
Marvel Comics logo 
London Philharmonic Orchestra logo 
Bosch (BSH Group) logo 
Volkswagen logo 
Cisco logo 
Activision logo 
London 2012 Olympics and Paralympics logo 
Microsoft logo 
Apple logo 
Gatsby logo 
Plex TV logo 
LEGO logo 
Selfridges logo 
The World Economic Forum logo 
Made by Many logo 
AND Digital logo 
IMG Licensing logo 
Disney logo 
Boohoo Group logo 
Debenhams.com logo 
The Rolling Stones logo 
Wreel Agency logo 
Polestar logo 
MOSCOT logo 
Virgin Atlantic logo 
American Express logo 
The Guide Dogs for the Blind Association logo 
Style.com logo 
Macmillan Education logo 
Zara logo 
Boeing logo 
Valtech logo 
McCann Manchester logo 
Warwick Acoustics logo 
Nando’s logo 
Virgin Active logo
Latest Articles
Rewrite, Refactor, or Strangle? A Practical Decision Framework. Rewrite, Refactor, or Strangle? A Practical Decision Framework
A practical framework for choosing rewrite, refactor, or strangler paths, based on risk, delivery pressure, change cost, and organisational appetite.
Retention Theatre: Why Companies Lose Good Engineers Whilst Pretending to Listen. Retention Theatre: Why Companies Lose Good Engineers Whilst Pretending to Listen
Retention theatre explained through surveys, recognition schemes, pay, autonomy, trust, workload, management quality, and why strong engineers still leave.
Why Transformation Programmes Fail After the Slide Deck. Why Transformation Programmes Fail After the Slide Deck
Why transformation programmes fail after the slide deck, covering ownership, governance, operating‑model change, vendor fragmentation, and delivery reality.
Technical AEO: Structuring Content for Direct Answers Without Creating FAQ Spam. Technical AEO: Structuring Content for Direct Answers Without Creating FAQ Spam
Structure technical AEO content for direct answers without FAQ spam, using extractable passages, visible text, schema discipline, and topic depth.
Building an LRU Cache in TypeScript: Hash Map and Doubly Linked List in Practice. Building an LRU Cache in TypeScript: Hash Map and Doubly Linked List in Practice
Build an LRU cache in TypeScript with a hash map and doubly linked list, then compare it with a simpler JavaScript Map implementation and O(1) operations.
Product Engineers and Software Engineers: What's the Difference? Product Engineers and Software Engineers: What's the Difference?
My view on product engineers and software engineers: how the remit differs, why organisational support matters, and what we need to learn after release.
How to Make Content Easier for Generative Engines to Trust. How to Make Content Easier for Generative Engines to Trust
How to make content easier for generative engines to trust, with clearer claims, stronger authorship, better sourcing, and structure that reduces ambiguity.
The Consultancy Rescue Loop. The Consultancy Rescue Loop
Consultancies can unblock stalled programmes, but without ownership transfer and internal capability growth, rescue work becomes recurring dependency.
The Deadline Debt Nobody Tracks. The Deadline Debt Nobody Tracks
Deadline debt explained as hidden rework, incidents, technical debt, quality loss, and recovery cost when teams compress quality without recording trade‑offs.
When Sass Colours Break After a Next.js Production Build. When Sass Colours Break After a Next.js Production Build
Diagnose Sass colours that survive compilation but break in Next.js production CSS when minification creates invalid mixed‑unit legacy rgb() values.
Mastering Server Components in Next.js. Mastering Server Components in Next.js
Mastering Server Components in Next.js, including client boundaries, data fetching, caching, streaming, and the mistakes that make App Router code messy.
The Engineering Capability Trap. The Engineering Capability Trap
Outsourcing can accelerate delivery, but if it replaces internal ownership, companies lose platform knowledge, leverage, and the ability to change safely.