Leo Liu, Developer in New York City, NY, United States
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Leo Liu

Verified Expert  in Engineering

Software Developer

New York City, NY, United States
Toptal Member Since
July 29, 2019

Leo is a full-stack developer, technology enthusiast, and University of Waterloo CS fellow. With a full-hearted pursuit in the web development field, Leo has led and engineered products in both React and AngularJS; built back ends in Ruby on Rails and Django; architected full-stack applications with REST or GraphQL; and leveraged databases, such as MySQL, Postgres DB, and Firebase, all with his peculiarly strict standards for Git commits.


Cedar Cares
Django, React, TypeScript, Apollo
Mitre Media
Apollo, GraphQL, Kubernetes, Docker, MySQL, React, Ruby on Rails (RoR), Ruby
JavaScript, CSS, HTML, PHP




Preferred Environment

Visual Studio Code (VS Code), Git, Linux, MacOS

The most amazing...

...project I have accomplished is migrating a 10-year-old codebase that faces millions of users.

Work Experience

Senior Software Engineer

2021 - PRESENT
Cedar Cares
  • Designed and deployed a pillar on-call procedure with an escalation process, risk assessment, and rotation that serves as the backbone of upholding high product quality and driving patient satisfaction levels past 90%.
  • Designed and led the implementation of a large-size product feature that allows millions of patients to submit client personalized registration forms effortlessly, proving value for the Cedar Pre product and improvement.
  • Navigated through difficulties, integrating with external vendors and the largest health system in South Caroline with millions of end users to a successful launch of the Cedar-Pre product, contributing to a contracted annual revenue of millions.
  • Managed and guided a software engineer intern on a client-facing, highly requested product feature to completion, providing an exceptional internship experience and growth opportunity.
  • Wrote extensive documentation and mentored all new engineers into the pillar, achieving increased engineering efficiency and satisfaction.
Technologies: Django, React, TypeScript, Apollo

Full-stack Developer

2018 - 2021
Mitre Media
  • Reduced server response time significantly, using different caching strategies, assets management, and database querying optimization in MySQL.
  • Architected and implemented a front-end system for a React application with MUI, styled components, and animation using React Pose.
  • Incorporated React strategies, such as higher-order components, render props, and global state management, using Apollo client caching.
  • Leveraged the proxy pattern in the back-end Ruby on Rails application to retrieve and process financial data through third-party REST APIs.
  • Migrated over 70% of the legacy codebase in PHP and Rails 3 to Rails 5 to a smart (dynamic) components architecture.
  • Proposed and developed a GraphQL endpoint for its advantage of a single data source while developing a GraphQL schema foundation in Rails and a reusable mutation query structure in React with Apollo.
  • Managed assets, using Webpacker in Rails for optimization.
  • Implemented an entire rebranded UI/UX on two major products that average one million monthly page views, using HTML (HAML), CSS (Tailwind.css), and JavaScript (Stimulus and EventQueue system, Webpack compiled) within two to three months.
Technologies: Apollo, GraphQL, Kubernetes, Docker, MySQL, React, Ruby on Rails (RoR), Ruby

Software Developer

2016 - 2017
  • Administered a reusable in-house web app to process issues and commit data from Redmine and Jira for SR&ED review, using a pure JavaScript solution.
  • Promoted code quality and standards by implementing various custom Git commit hooks.
  • Employed a PHP mass detector and PHP linting tools to maintain code integrity and visibility among the development team.
  • Streamlined developer workflow process by developing custom Jira development dashboards and queries.
  • Performed bi-weekly sprints, story point estimations, retrospectives, and code reviews in an agile manner.
Technologies: JavaScript, CSS, HTML, PHP

Cloud Apps Software Developer

2016 - 2016
  • Leveraged a UI/UX designer's expertise and excelled in redesigning Autodesk Fusion Life Cycle's main UI.
  • Initiated additional measures for page load time performance and UI improvements.
  • Strived for a detailed inspection of a peer code review and suggestive comments.
  • Skillfully practiced the use of AngularJS and SASS for feature development.
Technologies: Grunt, AngularJS

C/C++ Software Programmer

2015 - 2015
Fugawi Softwares
  • Created several in-house utilities, leveraging object-oriented architecture, parallel processing, and command line support.
  • Designed a graphical user interface for utilities, using Qt Creator with an MVC architecture.
  • Delivered projects using GDAL (Geospatial Data Abstraction Library), Boost, and Qt libraries for data processing and manipulation.
Technologies: Qt Creator, C++, C

Software Engineering

2015 - 2015
Imagine Communications Corp
  • Created a full record logging feature for all critical user interactions with the company's media software.
  • Identified and conducted fixes to software regarding 32 bits and 64 bits operating system discrepancies.
  • Operated and maintained version control using Mercurial and CVS.
Technologies: C#

Mobile App

❖ Established Facebook, email, and phone authentication using the Firebase authentication system.
❖ Handled storage and database using the Firebase cloud storage.
❖ Composed and designed a rich mobile front-end interface using React-Native for iOS and Android devices.
❖ Built reusable components throughout for simplicity and maintainability.
❖ Fluent with the Apple credentials set up and Testflight upload configuration using FastLane.
❖ Incorporated Crashalytics to monitor potential testing failures.
❖ Prepared to scale the application with a back-end REST API and Node.js for the web application.

University Club Website

❖ Designed and developed an informational website using a minimalistic theme.
❖ Ran the back end with Express.js and composed views with EJS (Embedded JavaScript).
❖ Hosted the application on an Amazon EC2 instance and routed it with Route 52.
❖ Utilized a semantics UI for visuals and a responsive design.
❖ Integrated an in-page PDF reader, feedback form submission, and Google API integration for location.


Ruby, JavaScript, Sass, CSS, GraphQL, HTML5, JavaScript 6, Java, TypeScript, CSS3, HTML, C#, C, PHP, C++, Python 3, Bash


Ruby on Rails (RoR), Tailwind CSS, AngularJS, Bootstrap, Cypress, React Native, Django, Flutter


React, REST APIs, JSON API, Node.js, Google Maps API


Jira, Git, RSpec, Docker Compose, JSS, Grunt, Qt Creator, Webpack 4, Babel


Agile Software Development, Continuous Integration (CI), Continuous Development (CD), REST, E2E Testing


Firebase, Visual Studio Code (VS Code), Web, Netlify, MacOS, Linux, Docker, Kubernetes


Freelancing, Gatsby, Semantic UI, Apollo, Networking, Artificial Intelligence (AI), Machine Learning


MySQL, MongoDB

2012 - 2017

Bachelor's Degree in Computer Science

University of Waterloo - Waterloo, Ontario, Canada