Back to site

Kristian Lonergan

Senior Frontend Developer

IrelandLinkedInGitHubkristianlonergan.com

Professional Summary

Senior Frontend Developer with over 10 years of experience building modern web applications. Currently acting as a line manager and code owner of two key applications at Propylon. Specialising in React, TypeScript, and modern frontend tooling, with a strong focus on code quality, mentorship, and delivering reliable, user-centred products.

Technical Skills

Frontend:React, TypeScript, JavaScript, HTML5 / CSS3, Next.js, Tailwind CSS, Material UI
State Management:Zustand, Redux, React Query, Context API
Testing:Playwright, Vitest, Jest, React Testing Library, Cypress
Tools & Workflow:Git, Vite, Storybook, Figma, CI/CD, Office.js
Leadership & Delivery:Line Management, Code Ownership, Code Reviews, Technical Mentorship, Contractor Oversight, Agile / Scrum

Work Experience

Propylon

January 2024 - Present

Senior Frontend Developer

January 2024 - Present
  • Code owner of the Request System (web) and its mobile application, overseeing architecture and feature delivery
  • Acting line manager with responsibility for team members and oversight of external contractors
  • Lead bi-weekly code reviews and provide technical mentorship across the frontend team
  • Migrated the E2E test suite from Cypress to Playwright, improving reliability and speed
  • Develop Microsoft Word add-ins with Office.js and React; drive frontend best practices and documentation

Rezexe

March 2020 - December 2023

Senior Frontend Developer

January 2022 - December 2023
  • Led frontend development for a high-traffic marketplace platform using React, TypeScript, and Material UI
  • Architected a Next.js monitoring dashboard for AWS container health with real-time updates
  • Established CI/CD pipelines, code review practices, and frontend documentation standards
  • Designed and implemented E2E testing strategy using Cypress

Frontend Developer

March 2020 - December 2021
  • Built key features for a marketplace platform with React, TypeScript, and Material UI
  • Created a reusable component library and integrated REST APIs with Redux and React Query
  • Delivered comprehensive unit tests with Jest and React Testing Library

Career Break

September 2019 - February 2020

European Travel & Professional Development

September 2019 - February 2020
  • Travelled across Europe, attended tech meetups, and completed online courses in modern web technologies

IBM

June 2014 - August 2019

Software Engineer

April 2017 - August 2019
  • Developed enterprise web applications and led migration from legacy Dojo to modern JavaScript frameworks
  • Built Java backend services and RESTful APIs; mentored junior developers across global teams
  • Created proof-of-concept applications using React and modern tooling

Software Test Engineer

June 2015 - March 2017
  • Designed automated test frameworks with Java and Selenium, significantly reducing manual testing effort
  • Maintained CI test suites and conducted performance testing to identify bottlenecks

Software Test Engineer Intern

June 2014 - May 2015
  • Developed and maintained automated test suites using Java and Selenium within an Agile team