David Leong, Software Developer in Tacoma, WA, United States
David Leong

Software Developer in Tacoma, WA, United States

Member since November 13, 2017
David is a full-stack engineer with over 12 years of experience in web development, managing all aspects of the development process. He's worked on 50+ projects and solved complex business problems in various industries including marketing, healthcare, eCommerce, real estate, and car insurance. David has consistently saved costs while increasing profits. He's ready for an opportunity to use his skills to grow your revenue exponentially.
David is now available for hire




Tacoma, WA, United States



Preferred Environment

Slack, SourceTree, Git, VS Code, MacOS

The most amazing...

...thing I've built is a web app for Amazon merchants that analyzes and optimizes ads activities to maximize performance and efficiency using React and Django.


  • Senior Full-stack Developer

    2019 - 2020
    SaveMySales (via Toptal)
    • Built a managed SMS marketing platform for brands.
    • Improved the developer experience by optimizing the build speed of webpack for live change.
    • Implemented the feature of segmenting customers for SMS campaigning.
    • Implemented the feature of scheduling SMS campaign with SMS segment splitting preview.
    • Worked with designers to resolve UI/UX problems, improve operations, and provide exceptional customer service.
    Technologies: Sentry, Datadog, GitLab CI/CD, Monorepos, Twilio, Rollup, Docker, MySQL, TypeORM, MUI (Material UI), TypeScript, Webpack, React
  • Senior Full-stack Engineer

    2019 - 2019
    DeciBio Consulting LLC
    • Worked as a lead developer overseeing the development of medical articles feed web app.
    • Implemented full-text search of articles using Elasticsearch.
    • Implemented live reloading of new feed content using socket.io.
    • Built front-end UI/UX using React and Redux.
    • Built back-end API using Hapi framework.
    • Managed deployment of web app using AWS.
    • Worked with designers to resolve UX problems, improve operations and provide exceptional customer service.
    Technologies: Amazon Web Services (AWS), AWS, React, Socket.IO, Elasticsearch, Hapi.js, Node.js
  • Senior Web Engineer

    2018 - 2019
    Yuzu Solutions LLC (via Toptal)
    • Served as a lead developer for building an educational marketing simulation app using Django, React, Redux, Crossbar, and Autobahn.
    • Worked in a SCRUM team.
    • Collaborated with data scientists and back-end developers to determine the best UI/UX.
    • Re-skinned the app with new theme and design.
    • Upgraded React from v15 to v16 enabling use of hooks.
    • Implemented an Excel-like form with excellent UX.
    • Ensured security of codebase by fixing npm package vulnerabilities.
    Technologies: Redux, React, Django, Python
  • Senior Full-Stack Engineer

    2018 - 2018
    PrepLink (via Toptal)
    • Worked on building accounting freelancing website for firms using Laravel, Vue.js and MySQL.
    • Built back-end APIs using Laravel best practice.
    • Implemented full-text search using Elasticsearch.
    • Wrote many reusable Vue.js components using best practice.
    • Improved old-fashioned Vue.js components with modularity and DRY principles in mind.
    • Set up JavaScript code linting and auto-formatting system using ESLint and Prettier.
    • Improved code design.
    Technologies: Elasticsearch, Bootstrap, SCSS, HTML, Vue, Laravel
  • Full-stack Web Engineer

    2018 - 2018
    Scoutible (via Toptal)
    • Worked on building game-based platform to assess a candidate's soft skills and increase the odds of a successful hire.
    • Improved outdated APIs written in Python.
    • Improved Python codebase design by adding reusable base classes based on design pattern.
    • Improved code design using React.js and Redux-saga standard practice.
    • Managed deployment process using GAE.
    • Improved storing app state info in local storage to use redux store.
    • Upgraded outdated npm packages.
    Technologies: Google Cloud Datastore, Google App Engine, Redux-Saga, Redux, React, JavaScript, Python
  • Senior Full-stack Web Engineer

    2017 - 2018
    VolKno (via Toptal)
    • Worked on building movie trailer rating web app.
    • Wrote Python background worker scripts that mines and feeds into database daily.
    • Worked with data scientists to resolve database design problems and provide exceptional customer service.
    • Improved interacting with MySQL using SequelizeORM.
    • Implemented full-text search for movie plot using Elasticsearch.
    • Improved analytics charts using D3.js and Highcharts.js.
    • Integrated video player.
    • Optimized complex database queries.
    • Improved outdated react-boilerplate codebase.
    Technologies: Elasticsearch, MySQL, Sequelize, Express.js, Node.js, Python, Highcharts, D3.js, Redux, React
  • Senior Full-stack Web Developer

    2015 - 2017
    • Developed RESTful APIs for music/video commerce web app using Django-Rest-Framework.
    • Contributed to building APIs for recruiting CRM web app using Flask and SQLAlchemy.
    • Developed 5+ SPAs using React/Redux.
    • Developed GraphQL API using Node.js, Express.js and MongoDB.
    • Advocated interaction design best practices with a focus on consistency and usability.
    • Built reusable React.js and Vue.js components.
    • Reviewed the pull requests submitted from other front-end developers.
    • Improved live update of app state by using websocket channel events broadcast.
    • Collaborated with the design team to define data structure.
    • Provided consultation on functionality design and technologies to adopt.
    Technologies: Node.js, Flask, Django, Python, Ruby on Rails (RoR), Ruby, Vue, Angular, MobX, Redux, React
  • Senior Full-stack Web Developer

    2012 - 2015
    • Built RESTful APIs using Flask and SQLAlchemy.
    • Wrote utility scripts in Python.
    • Integrated Webpack and React.js into Rails framework.
    • Collaborated with UI/UX team.
    • Ensured the technical feasibility of UI/UX designs.
    • Integrated and customized Material UI into AngularJS project.
    • Took part in making decisions on technologies to use.
    • Contributed to 3 Django applications.
    • Contributed to 3 Rails applications.
    • Reviewed the pull requests submitted from other developers.
    • Assured that code quality is above par using code linting tools.
    Technologies: Django, Node.js, Webpack, AngularJS, Vue, React, Laravel, Flask, Python, Sinatra, Ruby on Rails (RoR), Ruby
  • Full-stack Web Developer

    2008 - 2012
    Waveguide LLC
    • Served as a full-stack developer using Python, PHP, HTML, CSS and Javascript.
    • Built RESTful APIs using Flask and SqlAlchemy.
    • Created semantic HTML pages.
    • Confirmed that all user input was validated before submitted to back-end.
    • Ensured software compliance with specified standards.
    • Contributed to deployment to hosting server.
    • Implemented page designs in standards-compliant dynamic XHTML and CSS.
    • Maintained reusable components repositories.
    • Researched new support technologies for development goals.
    Technologies: SQLAlchemy, Flask, JavaScript, CSS, HTML, Python, Laravel, PHP


  • Matching Therapeutics to Cancer Patients

    The MatchTx solution was built to utilize the proprietary algorithms for several different objectives and market segments.

    I was responsible for the doctors facing app, which predicts how well the patient will respond to a drug, or which treatment is best, based on characteristics and outcomes of the best-matched cohorts.

    The front-end is built in SPA using React.js.
    The backend provides RESTful APIs to the front-end app and is built with Django-rest-framework.

    Overall, my contributions were:
    - Built the front-end web app using React.js.
    - Implemented graph drawing using highchart.js.
    - Built RESTful APIs using Django rest framework.
    - Implemented the algorithm that predicts biopsy matching the patient using Kaplan Meier estimator.

  • Slack-like Text Messaging Web and Mobile App

    Text messaging web app for healthcare teams.

    It is a care coordination platform for healthcare teams, where patients and medical staff can interact.

    My contributions were:
    - Integrated Redux store management into React.js codebase.
    - Closely worked with back-end developers to optimize existing Web technology and create the best possible user experience.
    - Advocated Web interaction design best practices, with a focus on consistency and usability.
    - Built reusable React.js components.
    - Reviewed the pull requests submitted from other front-end developers.
    - Improved live update of the app state by proper handling of WebSocket channel events broadcast.
    - Collaborated with the design team to define the data structure.
    - Provided consultation on functionality design and technologies to adopt.

  • Sell Photography Online

    This project involved developing online photo storefront.

    Here is how it works:
    1. Set up and upload images
    2. Promote gallery
    3. Sell images
    4. Fulfill orders
    5. Get paid for orders

    As a front-end developer, I built the web app in SPA using Vue.js library.

    My responsibilities were:
    - Build a webpack hot-reload config and gulp tasks system
    - Manage web app store using vuex
    - Implement image uploading and cropping
    - Integrate payment system using Stripe
    - Build base CSS stylesheets


  • Languages

    PHP, ECMAScript (ES6), GraphQL, JavaScript, HTML, CSS, SCSS, SQL, Python, Ruby, TypeScript
  • Frameworks

    Ionic, Laravel, Serverless Framework, Jest, Flux, Bootstrap 3, Express.js, Flask, Django REST Framework, Vuetify, Angular Material, Protractor, Jasmine, Ruby on Rails (RoR), Redux, Django, Angular, MUI (Material UI), AngularJS, Hapi.js, Loopback, Nuxt.js, Relay, OAuth 2, Sinatra, Bootstrap
  • Libraries/APIs

    Ruby on Rails API, jQuery, Backbone.js, Vuex, Vue Material, React Router, React Redux, Devise, Redux Form, MobX, Pundit, Material 2, Socket.IO, Sidekiq, Reactstrap, Nokogiri, Flask-RESTful, Chai, SQLAlchemy, REST APIs, Nightwatch.js, Redux-Saga, React, Node.js, Vue, Highcharts, Antd, Formik, API Development, D3.js, OmniAuth, RxJS, Facebook API
  • Tools

    Cucumber, Amazon Virtual Private Cloud (VPC), Bundler, AWS SES, Webpack, Pytest, RSpec, Angular CLI, Karma, Git, Capistrano, Mocha, Redux Thunk, VS Code, Amazon ECS (Amazon Elastic Container Service), RabbitMQ, Logstash, Auth0, AWS SDK, Kibana, Amazon SQS, SourceTree, Slack, Rollup, GitLab CI/CD, Sentry, Sequelize
  • Paradigms

    Functional Programming, Test-driven Development (TDD), Agile Software Development, Kanban, Behavior-driven Development (BDD), Scrum
  • Platforms

    MacOS, Red Hat Linux, Celery eCommerce, Heroku, AWS Lambda, Blockchain, Docker, Firebase, Ubuntu, Linux, Ubuntu 14.04, Ethereum, Twilio, Google App Engine, Amazon Web Services (AWS)
  • Storage

    PostgreSQL, MySQL, Elasticsearch, MongoDB, Redis, Amazon DynamoDB, Datadog, Google Cloud Datastore
  • Other

    Styled-components, Serverless, Amazon API Gateway, Axios, Enzyme, Apollo, TSLint, ESLint, RESTful Web Services, GitFlow, Vue-router, Bootstrap UI, Front-end Development, eCommerce, Web Development, Software Development, Bitcoin, Ethereum Smart Contracts, TypeORM, Monorepos, AWS


  • Bachelor's Degree in Computer Science
    2005 - 2008
    California State University - Los Angeles, California, USA

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