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Principal Software Engineer
London, United Kingdom

BENJAMIN CEGLOWSKI

Front End
Full Stack
Accessibility
Performance
About

Building software
that scales

Principal Full Stack Engineer with 20+ years' experience building high-performance web applications. I specialize in React ecosystems, design system architecture, and leading cross-functional engineering teams to deliver products used by millions.

Passionate about the intersection of engineering excellence and design craft. I believe great interfaces are invisible — they get out of the way and let people accomplish what they came to do.

Currently focused on performance at scale, developer experience & accessibility.

Experience

Where I’ve
Made Impact

HARMONIC SECURITY

2025 — Present
Principal UI Engineer
  • —Principal UI Engineer at a fast-paced AI startup, responsible for delivering the core product interface end-to-end.
  • —Architect and ship high-quality React applications at speed using React and Vite, balancing rapid iteration with production-grade robustness and performance.
  • —Drove significant frontend performance improvements, reducing load times and runtime overhead while maintaining a refined, responsive user experience.
  • —Instrumental in streamlining developer experience (DX), introducing tooling, build optimisations, and workflow improvements that accelerated development velocity across the team.
  • —Reduced product friction through thoughtful UI architecture, interaction design, and systematic refactoring, enabling faster feature delivery with fewer regressions.
  • —Established frontend standards and patterns that improved maintainability, consistency, and long-term scalability in a high-growth environment.

DELIBERATE SOFTWARE LTD

2021 — Present
Lead Consultant Software Engineer
  • —Design and deliver end-to-end web solutions for clients across e-commerce and fintech. Principal-level technical leadership, mentoring, architecture, and strategic guidance.
  • —Perfect Moment — Full production and upkeep of e-commerce platform: TypeScript, Next.js, GraphQL, Clojure, Contentful, Commercetools.
  • —Moo — Full-stack services for checkout and back-end PIM integration: TypeScript, Next.js, AWS, Salsify, Commercetools.
  • —Ebury — Trading application: TypeScript, Next.js, Python, PostgreSQL, AWS; hands-on mentorship and technical direction.

CRAFTING THE INTERNET LTD

2018 — 2021
Founder · Director · Technical Lead
  • —Software engineering and technical leadership across transport, education, energy, and compliance. End-to-end architecture, mentorship, and best practices.
  • —Riskbase — Lead engineer for mobile risk-assessment app (TypeScript, React Native). Shell Agile Hub — Logistics tracking platform (TypeScript, React, GraphQL, Node.js, Azure). EF — Scheduling platform for language tuition (TypeScript, React, MobX, Go). Trainline — International rail travel features (TypeScript, React, Redux, Node.js, C#).

ONEFINESTAY

2016 — 2018
Senior Full Stack Engineer
  • —Drove development of a new statically rendered React application architecture for the main platform.
  • —Advised product, SEO, and CRO teams; led migration from costly SaaS tools to in-house replacements.
  • —Full-stack: JavaScript, React, GraphQL, Node.js, Python, Django, AWS, Jest.

PHUSE.CA

2014 — 2016
Head of Engineering
  • —Led distributed, asynchronous engineering team delivering bespoke web consultancy.
  • —Oversaw project delivery and code quality across JavaScript, PHP, React, Node.js, Angular, Vue.js, MySQL.
  • —Implemented company-wide engineering standards and best practices; architected full-cycle applications.

THE BIO AGENCY

2012 — 2013
Senior Software Engineer · UI Team Lead
  • —Led front-end team developing web platform for Yell Group. Technical leadership, mentorship, training.
  • —JavaScript, HTML, CSS, PHP, MongoDB, Backbone, Ember (LAMP).

SHINE MARKETING

2011 — 2012
Web Software Engineer
  • —Developed end-to-end retail e-commerce websites for a London-based boutique consultancy.
  • —Delivered full-stack solutions using PHP, MySQL, JavaScript, HTML, CSS, and jQuery.

FREELANCE

2006 — 2011
Web Software Engineer
  • —Delivered web design and development services for several Durban and London-based consultancies.
  • —Provided full-stack engineering across JavaScript, PHP, MySQL, Apache, and MongoDB, creating performant and maintainable digital solutions for clients.
Technical Skills

Tools of
the Trade

Languages
  • TypeScript
  • JavaScript
  • HTML5
  • CSS3
  • GraphQL
  • SQL
Frameworks
  • React
  • Next.js
  • Remix
  • Node.js
  • Astro
  • Svelte
Tools
  • Webpack
  • Vite
  • Figma
  • Git
  • Docker
  • CI/CD
Practices
  • Design Systems
  • A11y
  • Perf Optimization
  • TDD
  • Code Review
  • Mentorship
Notable Work

Selected
Projects

HARMONIC SECURITY

Principal engineering across the user interfaces of every software product released by this fast-paced AI security startup.

ReactTypeScriptVitePlaywright

PERFECT MOMENT LTD

Led full production and upkeep of the e-commerce platform. Integrated TypeScript, Next.js, GraphQL, Clojure, Contentful, and Commercetools for a performant, maintainable solution.

Next.jsGraphQLClojureCommercetools

TRAINLINE

Rolled out multi-leg European journeys for Trainline's 'Single Global Product'.

ReactTypeScriptNode.jsRxJSRedux

ONEFINESTAY

Drove new statically rendered React architecture. Advised product and SEO teams; led migration from SaaS tools to in-house replacements.

ReactGraphQLDjangoAWS
Education

Durban University of Technology

Bachelor of Technology (Distinction)
2006 — 2010

Kearsney College

Matric (IEB Higher Grade)
2005
Get in Touch

Let’s Build
Something
Great

Portfolioceglow.ski
LinkedInlinkedin.com/in/benceglowski
© 2026 Benjamin Ceglowski