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Diego Sieg

Senior Front-End Software Engineer · 14+ Years Experience

diegosieg@gmail.com · diegosieg.dev · Christchurch, New Zealand

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Professional Summary

Results-driven Senior Front-End Engineer with 14+ years delivering high-quality web applications at scale. Deep expertise in React, TypeScript, and modern JavaScript ecosystems, with a strong track record of modernising UI stacks, building design systems, and improving developer experience through robust tooling and automated testing. Experienced in agentic AI development (Claude Code, Copilot, Cursor) and well-versed in cross-functional collaboration, mentorship, and data-driven product decisions. Trilingual (English/Brazilian Portuguese/Spanish) with a background spanning journalism, digital media, and business innovation.

Core Skills

Front-End
React.js, TypeScript, Next.js, Vue.js, Redux (Sagas/Thunk), GraphQL, React Query, Vite, Webpack, MicroFrontend, Web performance, Cross-browsers development, Accessibility, Progressive Enhancement development, AB tests
Testing
Jest, Vitest, React Testing Library, Cypress, Playwright, Storybook, Chromatic, MSW
Styling
CSS3, Sass, Styled Components, CSS-in-JS (JSS), Animation, Material UI, Tailwind, Bootstrap
Agentic AI Dev
Claude Code, GitHub Copilot, Cursor, Windsurf, Codex
Observability
New Relic, SLOs, Alerting, Sumo Logic, Pagerduty, Rootly, LaunchDarkly, Mixpanel, Pendo
DevOps / Cloud
AWS, Docker, GitHub Actions, TeamCity, SonarQube, Terraform, CI/CD pipelines
Full Stack
C# .NET, Node.js, REST APIs; familiarity with Ruby on Rails, and Python
Soft Skills
Technical leadership, mentoring, agile (Scrum/Kanban), problem-solving, analytical skills, async remote collaboration, great attention to detail and fast learner
General
Experience in Product Engineering and Management, Business Development, and Design Systems. Familiarity with design and collaboration tools, such as Miro, Figma, Slack, Glean, Gemini, NotebookLM, Jira, and Confluence

Work Experience

Senior Front-End Software Engineer

Xero (xero.com)

Mar 2020 – Present · Remote, New Zealand

Leading UI/UX Engineering: Successfully driving the team to develop and deliver top-quality product experiences for customers, taking into account accessibility, responsiveness, and performance improvements across a wide range of projects and initiatives.

  • •Recently led UI/UX engineering for the Xero Partner Hub Navigation initiative, delivering a unified experience across Xero HQ and Xero Practice Manager for thousands of accounting partners.
  • •Drove agentic AI development: created shareable and reusable skills and prompt instructions for different AI harnesses and agents (Claude Code, Copilot, Cursor); promoted automation to address tech debt; and contributed best practices and knowledge sharing across teams.
  • •Drove front-end architecture modernisation: migrated legacy design system versions, upgraded React and Webpack, and introduced micro-frontends — significantly improving performance, maintainability, and developer velocity.
  • •Established automated testing pipelines (Jest, Vitest, Playwright) and introduced Storybook + Chromatic for visual/accessibility testing, reducing regression risk and improving component reusability.
  • •Implemented observability best practices via New Relic dashboards, SLOs, and alerting, enabling the team to detect and resolve incidents faster.
  • •Mentored graduates, junior, and intermediate engineers in front-end patterns, testing, and best practices, accelerating their professional growth.
  • •Championed data-driven product decisions by collaborating with Product and Design on UI event tracking (Mixpanel, Pendo, Intercom/Appcues) and key metric definitions.
  • •Improved cross-functional collaboration by driving tighter designer-engineer feedback loops and async communication practices in a remote/hybrid setting.

Front-End Developer

NV Interactive (nvinteractive.co.nz) / NV Play (nvplay.com)

Jun 2019 – Mar 2020 · Remote / Christchurch, NZ

  • •Built websites and large-scale web apps using Vue.js, Vuex, React.js, Highcharts, GSAP, Webpack, and Gulp.

Front-End Developer

Verizon Connect (verizonconnect.com)

Feb 2018 – May 2019 · Christchurch, New Zealand

  • •Developed business-intelligence web applications featuring rich data visualisations (Highcharts, d3.js) using React, Redux, TypeScript, JSS, and Jest in an agile team.

Front-End Developer (Web & Native Apps)

NV Interactive (nvinteractive.co.nz)

Apr 2015 – Feb 2018 · Christchurch, New Zealand

  • •Delivered web applications across a wide range of clients using Angular, Vue.js, Knockout, d3.js, and Highcharts.
  • •Developed cross-platform mobile apps for Android, iOS, and Windows using Xamarin/C# and Cordova.

Front-End Web Developer

The Space in Between / Marker Studio

Apr 2014 – Jan 2015 · Auckland, New Zealand (contract)

  • •Delivered front-end work for 15+ client projects across .NET and PHP environments (Kentico, Orchard, WordPress) using JavaScript, Angular, Sass, and HTML5.

Front-End Developer & Innovation Product Leader

Designa (designa.com.br)

Jun 2013 – Apr 2014 · São Paulo, Brazil

  • •Built modern web applications and validated MVPs using Design Thinking and Lean UX methodologies.
  • •Led business model generation for in-company startups; managed social media and digital marketing strategy.

Front-End & UX Developer

TOTVS (totvs.com)

Jan 2013 – Aug 2013 · São Paulo, Brazil

  • •Improved the UI/UX of a large-scale financial software used across Brazil; created a Developer Style Guideline and built real-time data visualisation prototypes.

Data Journalist & UX Developer

Editora Abril — Veja Magazine (veja.com.br)

Jun 2012 – Jan 2013 · São Paulo, Brazil

  • •Researched and developed data visualisation tools and new media products for Brazil's largest magazine, leveraging social media APIs and public data sources.

Education

Graduate Diploma in International Business Innovation (Level 7)

ICL Business School, Auckland, NZ · 2014–2015

Postgraduate Diploma in Digital Media & Data-driven Journalism (Level 8)

Faculdade Cásper Líbero, São Paulo, Brazil · 2009–2011

Bachelor's Degree in Media Communication & Journalism (Level 7)

Universidade de Taubaté, São Paulo, Brazil · 2003–2006

Professional Development

  • •Internal AI Tools Training (Claude Code, Copilot, Cursor, Windsurf) — Xero, 2025/2026
  • •Build DeepSearch in TypeScript / LLM Agent Skills — aihero.dev (Matt Pocock), 2025
  • •Rapid Software Testing Explored — Michael Bolton, 2025
  • •CSS for JS Developers & The Joy of React — Josh Comeau, 2024
  • •Total TypeScript — Matt Pocock, 2023
  • •Level up with React Query — ui.dev/react-query, 2023
  • •AWS Cloud Practitioner Essentials — AWS, 2022
  • •Crucial Conversations Training — Xero, 2020
  • •Epic React & Testing JavaScript — Kent C. Dodds, 2020
  • •React Hooks, Modern and Advanced Javascript, TypeScript — ui.dev, 2019
  • •Advanced React and GraphQL — Wesbos.com, 2019
  • •React Nanodegree — Udacity, 2017–2018
  • •Web Development — Howtocode.com.br and DRC.com.br — São Paulo, Brazil, 2011 - 2014
  • •Agile Project Management (SCRUM) — Caelum.com.br, São Paulo, Brazil, 2011
  • •Technician in Web Design & Multimedia — Senac.br, São Paulo, Brazil, 2007 – 2008

Honours & Awards

  • •Best Product & Design — YouTube Developer Day 2013, Google Brazil
  • •Best App for Google Chrome — Hackathon, Google Brazil, 2013
  • •Top 5 Best Designs Nominee — TNW Brazil Startup Award, 2012
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