I’m a Senior Frontend Developer with over 10+ years delivering scalable, high-performance web and mobile applications across Europe and the UK, specialising in TypeScript, React, React Native (Expo), Next.js, GraphQL and modern frontend architectures (Monorepos, NX, Jotai/Redux). I care deeply about product quality and user experience, with a track record shipping features for teams and award-winning platforms (e.g., Virgin Trains Ticketing, Heycar) and large-scale products (e.g., Shell, Pickswise). I also lead product and technical strategy as a founder (AMiSi.ai), and I’m experienced in performance, SEO, accessibility, and DevOps workflows (CI/CD, build pipelines, and deployment automation).

Simon Wierzchowski

I’m a Senior Frontend Developer with over 10+ years delivering scalable, high-performance web and mobile applications across Europe and the UK, specialising in TypeScript, React, React Native (Expo), Next.js, GraphQL and modern frontend architectures (Monorepos, NX, Jotai/Redux). I care deeply about product quality and user experience, with a track record shipping features for teams and award-winning platforms (e.g., Virgin Trains Ticketing, Heycar) and large-scale products (e.g., Shell, Pickswise). I also lead product and technical strategy as a founder (AMiSi.ai), and I’m experienced in performance, SEO, accessibility, and DevOps workflows (CI/CD, build pipelines, and deployment automation).

Available to hire

I’m a Senior Frontend Developer with over 10+ years delivering scalable, high-performance web and mobile applications across Europe and the UK, specialising in TypeScript, React, React Native (Expo), Next.js, GraphQL and modern frontend architectures (Monorepos, NX, Jotai/Redux).

I care deeply about product quality and user experience, with a track record shipping features for teams and award-winning platforms (e.g., Virgin Trains Ticketing, Heycar) and large-scale products (e.g., Shell, Pickswise). I also lead product and technical strategy as a founder (AMiSi.ai), and I’m experienced in performance, SEO, accessibility, and DevOps workflows (CI/CD, build pipelines, and deployment automation).

See more

Experience Level

Expert
Expert
Expert
Expert
Expert
Expert
Expert
Expert
Expert
Expert
Expert
Intermediate
See more

Language

Polish
Fluent
English
Fluent
German
Beginner

Work Experience

Senior React Native / Full-Stack Frontend Developer at GamScore
April 1, 2026 - June 30, 2026
Built and owned the GamScore mobile front-end end-to-end using an Expo React Native starter kit to establish a scalable, production-ready architecture. Set up and maintained an Nx monorepo covering the mobile app, shared UI/components, Backend-for-Frontend (BFF) layer, deep link router, and tooling. Implemented screens, reusable components, navigation flows, and feature modules with React Native, Expo Router and TypeScript. Designed and implemented a Node.js/Fastify BFF consuming upstream endpoints and shaping API contracts. Built a deep link router handling deep links and providing fallback web pages when the app isn’t installed. Configured CI/CD (GitHub Actions, Expo Application Services, EAS Build/Submit) and deployment workflows to Apple App Store Connect/TestFlight and Google Play internal testing. Integrated RevenueCat for subscription management and configured sandbox testing across environments. Owned build profiles, signing, environment configuration, release channels and st
Senior React Native Developer at Francis
November 1, 2025 - April 30, 2026
Led end-to-end delivery of core production fintech mobile features focusing on conversational AI experiences, secure onboarding/authentication, account lifecycle reliability, and analytics-driven instrumentation. Built and evolved a modular chatbot architecture for “Tell Francis” including flow/session runtime, SSE streaming responses, persisted chat summaries, and route-safe action handling. Improved AI chat reliability by preventing duplicate submissions, hardening async mutation states, and stabilising navigation/highlight behaviour after account creation. Implemented app gating across authenticated areas (auth, email verification, biometrics, onboarding, and freemium/paywall checks). Simplified email verification and deep-link handling with app-state-driven checks to reduce polling. Added analytics instrumentation for key account events and handled edge cases like empty-state behaviour after account deletions. Strengthened error handling for streamed assistant messages (abort/e
Senior Software Engineer at Heycar UK
April 30, 2025 - July 22, 2025
Delivered major site features using React, Next.js, and GraphQL. Improved site performance and SEO through Jotai and server-side optimizations. Implemented A/B testing framework using Flagr. Developed automated testing workflows with Cypress.
Senior Software Engineer at Heycar UK
April 30, 2025 - July 22, 2025
Delivered major site features using React, Next.js, and GraphQL. Improved site performance and SEO through Jotai and server-side optimizations. Implemented A/B testing framework using Flagr and developed automated testing workflows with Cypress.
Founder / Product Lead at AMiSi.ai
January 1, 2024 - Present
Founded AMiSi.ai, a SaaS platform enabling creators, marketers, and businesses with AI tools for image/video generation, content editing, and automation. Owned product vision, technical strategy, and UX across a modular AI suite (text-to-image, image-to-image, text-to-video, AI avatars, and more). Built the frontend with React/Next.js/TypeScript and Tailwind, integrated AI providers via APIs (OpenAI, Stability AI and custom fine-tuned solutions), and implemented a credit-based subscription system with Stripe including real-time usage tracking. Delivered authentication/analytics/feedback mechanisms to drive iteration, and ran early-access collaboration plus marketing automation experiments (email funnels, social sharing incentives, affiliate systems).
Senior React Native Developer at Virgin Trains Ticketing
June 30, 2023 - July 22, 2025
Built award-winning Virgin Trains Ticketing App using React Native. Enhanced mobile user experience and maintained high test coverage. Led code reviews and mentored junior developers.
Senior React Native Developer at Virgin Trains Ticketing
June 30, 2023 - July 22, 2025
Built award-winning Virgin Trains Ticketing App using React Native. Enhanced mobile user experience and maintained high test coverage. Led code reviews and mentored junior developers.
Senior React Native Developer at Virgin Trains Ticketing
October 1, 2022 - June 30, 2023
Joined Virgin to support the new Virgin Trains Ticketing App, which later received awards. Developed and implemented new features using React Native. Collaborated with design and product teams to ensure seamless UX. Covered components and user journeys with unit and E2E tests, and conducted code reviews providing technical guidance to junior developers.
Senior Software Engineer at heycar UK
February 1, 2021 - April 30, 2025
Delivered large features by assessing risks, blockers and scope. Worked intensively with GraphQL, Node and Express to reduce API complexity. Ensured release stability through Cypress testing for core site areas. Worked in Kanban for flexible prioritisation and feature readjustments. Implemented Flagr for feature A/B testing and to prevent bugs from major changes. Improved performance, speed and SEO by using Jotai and Next.js to reduce unnecessary re-renders, and contributed across React/Next/GraphQL and modern testing/tooling. Collaborated within Agile delivery and release processes.
Senior Software Engineer at Cambridge Cognition Limited
December 31, 2020 - July 22, 2025
Developed hybrid mobile apps supporting brain health research. Created cognitive tests and improved digital health platforms using TypeScript, React, Redux.
Senior Software Engineer at Cambridge Cognition Limited
December 31, 2020 - July 22, 2025
Developed hybrid mobile apps supporting brain health research. Created cognitive tests and improved digital health platforms using TypeScript, React, and Redux.
Senior Software Engineer at Cambridge Cognition
August 1, 2020 - December 31, 2020
Joined a sprint team developing and maintaining hybrid mobile applications in the Digital Health space supporting researchers and health organisations globally. Built and enhanced hybrid apps using TypeScript and Capacitor runtime with a React/Redux architecture and custom Flux. Designed and implemented solutions to maximise value, added automated test coverage using Jest and Appium, and supported cognitive testing development (game-like tests). Improved user experience and platform architecture and development processes, and produced documentation demonstrating compliance with regulatory standards.
Senior React Native Developer at Clarizen
June 30, 2020 - July 22, 2025
Refactored and optimized a complex draggable Kanban board for cross-platform performance.
Senior React Native Developer at Clarizen
June 30, 2020 - July 22, 2025
Refactored and optimized a complex draggable Kanban board for cross-platform performance.
Senior React Native Developer at Virgin
February 29, 2020 - July 22, 2025
Developed mobile apps and BFF service layers using React Native, Redux, Node.js.
Senior React Native Developer at Virgin
February 29, 2020 - July 22, 2025
Developed mobile apps and BFF service layers using React Native, Redux, and Node.js.
Tech Lead & Senior Developer at Shell
November 30, 2019 - July 22, 2025
Led the mobile development of the Shell Fleet App (iOS & Android). Directed cross-departmental collaboration and optimized CI/CD pipelines.
Tech Lead & Senior Developer at Shell
November 30, 2019 - July 22, 2025
Led the mobile development of the Shell Fleet App for iOS and Android. Directed cross-departmental collaboration and optimized CI/CD pipelines.
Senior React Native Developer at Virgin
November 1, 2019 - February 29, 2020
Built and delivered an end-to-end mobile app using React Native and TypeScript. Created reusable themed components, designed and implemented Redux-based state management modules, and followed TDD with Jest and Enzyme. Added E2E tests using Detox and contributed to a BFF service layer in Node with TypeScript.
CTO & Co-Founder at Primepix
August 31, 2019 - July 22, 2025
Built a full-stack e-commerce platform (React Native, Node.js, AWS, GraphQL). Set up cloud architecture, DevOps pipelines, and payment integrations.
CTO & Co-Founder at Primepix
August 31, 2019 - July 22, 2025
Built a full-stack e-commerce platform using React Native, Node.js, AWS, and GraphQL. Set up cloud architecture, DevOps pipelines, and payment integrations.
Tech Lead (extended) at Shell (Shell Fleet App)
January 1, 2019 - November 30, 2019
Developed and led a global mobile application (Shell Fleet App for Android and iOS). Took lead responsibilities including preparing release candidates and releasing incremented app versions, planning capacity for additional features, supporting testers, triaging and splitting work between team members, and coordinating with other departments (Build, Marketing, Analytics, QA). Educated non-technical colleagues on technical possibilities, optimised processes, resolved bottlenecks, and built automated procedures. As a tech lead, built optimised scalable modular native mobile applications using React Native and Redux. Worked with REST APIs (swagger), native feature integrations (e.g., Face/Touch ID) and CI tooling (CircleCI/App Center), and contributed to app release processes including Apple Pay/Android Pay and App Store Connect/TestFlight.
Senior Developer at Lloyds Banking Group, ClearBank®, The Frameworks Spark, Runpath, Crate Enterprises
December 31, 2018 - July 22, 2025
Held senior developer roles working on React development for financial products, Vue.js development for banking applications, frontend development focusing on accessibility, UI consultancy, and responsive web development.
Senior React Native Developer at Shell (Shell Fleet App)
July 1, 2018 - January 31, 2019
Built the Shell Fleet app for Android and iOS using React Native and Redux. Interfaced with and mocked REST APIs (swagger), integrated native features (e.g., Face/Touch ID), and delivered modular scalable mobile architecture. Worked with CI tooling (CircleCI/App Center) and release workflows (Apple Pay/Android Pay, App Store Connect, certificates/provisioning profiles, TestFlight). Participated in Agile development and used tools such as Fastlane where applicable.
Senior React Developer at Lloyds Banking Group
February 1, 2018 - July 31, 2018
Launched new financial products and digital marketing initiatives (promotions). Extended functionality of existing web and mobile applications to attract and retain customers. Integrated third-party APIs. Secured, maintained and updated multiple repositories, and built responsive web pages using Bootstrap/Flow/React. Delivered modular well-tested front-end applications designed to scale with the business, contributing to engineering standards and knowledge sharing. Mentored junior front-end engineers and supported accessible, secure implementations across devices. Worked in an enterprise environment with automated build/test/release processes and version control (Git) plus change management (JIRA).
Senior Developer at Crate Enterprises
January 1, 2018 - July 22, 2025
UI Code Development, Responsive Web
Senior Developer at Runpath
January 1, 2018 - July 22, 2025
UI Consultancy, Dynamic Interfaces
Senior Developer at The Frameworks Spark
January 1, 2018 - July 22, 2025
Frontend Development, Accessibility Focus
Senior Developer at ClearBank®
January 1, 2018 - July 22, 2025
Vue.js Development, Banking Applications
Senior Developer at Lloyds Banking Group
January 1, 2018 - July 22, 2025
React Development, Financial Products
CTO / Co-Founder at Primepix
August 1, 2017 - August 31, 2019
Co-founded Primepix and led technical direction. Prepared a monorepo to share common code across ends. Set up the tech stack and CI/CD pipelines (CircleCI), testing distribution workflows (TestFlight/Google Play beta). Designed and developed backend APIs and schema using GraphQL (Prisma 2.0), implemented BFF services using Node (TypeScript + ES7), Yoga and GraphQL, and integrated AWS services (S3 and IAM policies). Built Stripe Connect subscriptions and payments, and integrated print-on-demand services. Developed front-end for Android/iOS using React Native with TypeScript and Apollo GraphQL and Jest/Enzyme tests; built web using React (TypeScript + ES7) and Apollo GraphQL with Jest.
Senior Vue.js Developer (extended) at ClearBank
April 1, 2017 - February 28, 2018
Developed cross-browser/cross-platform solutions with strong HTML5/CSS3/SASS experience. Implemented interactive front-end features using Vue.js/Vuex/Axios/Moment/Lodash/Element UI, and implemented portions using TypeScript. Worked with Webpack and integration with server-side code (C#/ASP.NET) to create dynamic pages. Designed data model structures and built RESTful API integrations. Contributed documentation and improved automation of documentation, shared knowledge with technical and non-technical teams, and discussed technical solutions with clients. Maintained focus on accessibility (AA standard), usability, and emerging technologies; used version control (TFS).
Front-end Developer at The Frameworks
September 1, 2015 - April 30, 2017
Provided front-end development and technical consulting across client projects. Produced responsive, cross-browser solutions with HTML5/CSS3/SASS and worked with template engines. Built interactive experiences using JavaScript and frameworks including jQuery and Angular/AngularJS/Vue/React with Redux. Used build systems/task runners like Gulp/Grunt/Webpack, wrote unit tests (Jasmine/Karma), and integrated server-side code to produce dynamic pages. Practiced accessibility (sites at least AA standard), REST API integration, and AJAX techniques. Also worked with PHP/Laravel and Blade templating, including email best practices and version control via Git.
CEO / Founder at Selcouth Digital (Selcouth Digital)
May 1, 2014 - Present
Lead strategy and objectives for a digital training and development organisation. Ensure financial sustainability and adapt strategy to opportunities and market changes. Manage relationships, partnerships, and staffing, including setting objectives, delegation, recruiting, contracts, coaching, and risk management. Develop and deliver a training portfolio based on industry needs, including quality control for trainers and sessions, and research funding sources and partners to support programmes. Maintain operations and ensure an innovation-focused culture.
UI Consultant at Runpath
April 1, 2014 - April 30, 2015
Produced and maintained websites and web application user interfaces. Worked closely with designers to convert Photoshop designs to working browser pages using semantic HTML/CSS. Collaborated with server-side developers to implement interactive database-driven experiences. Provided accurate delivery estimates, contributed to documentation, and trained other non-technical staff (especially designers). Maintained awareness of accessibility/usability and emerging technologies, contributed to development standards, and discussed technical solutions with clients.
UI Code Developer at Crate Enterprises
March 1, 2013 - March 31, 2014
Produced and maintained websites and web application user interfaces. Worked with designers to translate static Photoshop designs into browser-based pages using semantic HTML/CSS. Collaborated with server-side developers on interactive and database-driven websites, provided delivery estimates, and contributed to documentation/specification. Trained non-technical staff (particularly designers) and worked to maintain development standards and accessibility/usability awareness, while discussing solutions with clients.
Freelance Graphic & Web Developer at SIMON-W.co.uk
January 31, 2013 - July 22, 2025
Designed and developed web solutions for diverse industries.
Freelance Graphic & Web Developer at SIMON-W.co.uk
January 1, 2013 - July 22, 2025
Designed and developed web solutions for diverse industries.
Freelance Graphic Designer / Web Developer at Simon-W.co.uk
January 1, 2006 - January 31, 2013
Freelance web and graphic design work including building and uploading websites, choosing colours/text/background and page elements, discussing design with clients, positioning buttons/pictures/links, and testing website features.

Education

Add your educational history here.

Qualifications

Master of Technology (MTech), Web/Multimedia Management and Webmaster
January 1, 2002 - January 1, 2007
Expo / React Native Mobile Starter Pack (publication)
January 11, 2030 - August 4, 2026
MyMathsCloud (publication)
January 11, 2030 - August 4, 2026
AMiSi.ai (publication)
January 11, 2030 - August 4, 2026

Industry Experience

Software & Internet, Financial Services, Transportation & Logistics, Energy & Utilities, Healthcare, Retail, Media & Entertainment, Education, Professional Services