LeeEngineering
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Portfolio / 2026

Senior Fullstack Engineer

David Lee

Frontend Engineering · Backend Systems · Engineering Management

I build products from idea and architecture to production — connecting frontend, backend, and business thinking.

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Explore selected work
Case / 001Featured engineering task

Prepared for

3025.team

Fullstack test assignment

A focused engineering exercise spanning interface architecture, API design, data persistence and asynchronous processing.

Next.jsNestJSPostgreSQLRedisBullMQ
Open test assignment
06About

The work behind the title.

I enjoy turning complex requirements into clear, maintainable, and scalable products.

  1. 01

    I strive for excellent code while balancing quality, development speed, and actual product requirements.

  2. 02

    For me, development starts with understanding the problem, not writing code. It is important to understand which user and business need a feature addresses, not merely implement it.

  3. 03

    I design solutions to remain understandable, maintainable, adaptable, and scalable as the project grows.

  4. 04

    I work to make complex ideas clear and establish a shared language between engineering, product, and business.

02My expertise

One engineering perspective. Three operating modes.

Switch the system context to inspect how the same product challenge is approached from implementation to delivery.

01

System mode / Frontend

Interfaces engineered as systems

Architecture for complex product interfaces with explicit attention to performance, state and maintainability.

  1. 01React + Next.js / Vue + Nuxt
  2. 02TypeScript
  3. 03UI architecture
  4. 04State management
  5. 05Performance
  6. 06Complex interfaces
03Experience

What I have worked on

Projects I have contributed to and my role in them.

01
2024 - 2026
FrontendBackendManagement

Trading company | Tech Lead

An automated trading fintech platform built from the ground up.

Designed and implemented the web platform architecture, delivering the MVP single-handedly in three months. I then assembled the development team and introduced Scrum, establishing a regular and predictable feature delivery process. Built the core payment processing system. Introduced AI assistants (Cursor, Claude) into the team's daily workflow, reducing the time spent implementing boilerplate code.

TypeScript, Node.js, PHP, Laravel, Vue, Nuxt, PostgreSQL, Docker, RabbitMQ, Redis, Python, Litestar.

02
2022 - 2024
FrontendManagement

Zhili Byli | Frontend Team Lead

Product development of an MVP hotel booking service.

Developed and launched the MVP interface in production within two months, enabling the business to begin acquiring its first customers. Designed the React and Next.js architecture with SSR. Implemented data exchange between the interface and microservices through Apollo GraphQL, improving hotel-list rendering performance. Established code review processes and coding standards, reducing defects during testing.

TypeScript, React, Next.js, Apollo GraphQL, REST API, Storybook, Jest, Cypress, Nightwatch

03
2016 - 2022
FrontendBackend

Donatepay | Fullstack Developer

A high-load payment platform for streamers with over one million users and 100,000 daily transactions. Progressed from Junior Developer to Technical Team Lead.

Redesigned the platform's payment core, reducing new payment gateway integration time from two weeks to two days. Replaced the event delivery mechanism with WebSockets, lowering database resource utilization from 55% to 15%. Optimized complex SQL queries over tables containing one billion records, reducing API response time in high-load scenarios to 200 ms. Introduced asynchronous payout processing with RabbitMQ, eliminating the risk of duplicate financial transactions. Led a team of five developers, refactored 60% of the legacy codebase, and contributed to the migration from a monolith to microservices.

PHP, Laravel, TypeScript, Vue, WebSocket, Centrifugo, jQuery, Bootstrap, PHPUnit, Docker, MySQL, Elasticsearch, Redis

04
2018 - 2021
Backend

Ompniplace | Backend Developer

A startup building a CRM for gardening and homeowners associations.

Developed the backend for user accounts and the administration panel. Integrated payment solutions for utility bills. Built an ATM integration that read the platform's QR codes and automatically populated payment details and meter readings.

PHP, Symfony, PHPUnit, Docker, MySQL

04Work with me

Two ways to start a useful conversation.

01

For teams

Invite me to your team

For hands-on senior engineering, technical leadership and product-facing roles.

Discuss a role
02

For products

Build a product with me

For a website, service or product that needs strong technical execution from idea to release.

Discuss a project