Congwen Ma, Developer in San Francisco, CA, United States
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Congwen Ma

Verified Expert  in Engineering

Software Developer

San Francisco, CA, United States
Toptal Member Since
March 6, 2018

Congwen is a dedicated web developer specializing in developing full-stack web applications using practical frameworks. He's passionate about solving problems for others. A good solution to Congwen usually requires a dose of creativity that requires more effort to adapt and perfect.


Rally Health
Angular, Ruby on Rails (RoR), Scala, JavaScript
MongoDB, Ruby on Rails (RoR), JavaScript
PostgreSQL, AngularJS, React, Ruby on Rails (RoR), Ruby, JavaScript




Preferred Environment

Kubernetes, Amazon Web Services (AWS), Docker, Jenkins, Scala, Ruby on Rails (RoR), React, Bash Script, PostgreSQL, PostGIS

The most amazing...

...thing I've made was a Chrome DevTool extension that renders a visual tree graph of my company's proprietary framework.

Work Experience

Principal Software Engineer | Engineering Manager

2019 - PRESENT
Rally Health
  • Constructed solutions to solve business requirements in an efficient way.
  • Proposed and led data schema changes that improved the product with minimum effort, eliminating tech debts.
  • Led the engineering effort of developing a new product.
Technologies: Angular, Ruby on Rails (RoR), Scala, JavaScript

Full-stack Software Engineer

2018 - 2018
  • Built concrete Ruby on Rails APIs that carried out tasks via Node.js microservices.
  • Developed and implemented a strategy for migrating the front-end codebase to React additively.
  • Designed and implemented NoSQL solutions based on an in-house framework.
Technologies: MongoDB, Ruby on Rails (RoR), JavaScript

Software Engineer

2014 - 2018
  • Constructed a Chrome developer tool to help developers debug and analyze a proprietary state-management framework.
  • Used JSCodeshift (a JavaScript code-mod toolkit) to make application-wide code changes to replace deprecated APIs and code syntax.
  • Constructed middleware that allowed React to work with our proprietary model framework.
  • Built and analyzed an ad exchange platform with React/Angular 1 frameworks.
  • Developed friendly Ruby on Rails APIs for our front-end application.
Technologies: PostgreSQL, AngularJS, React, Ruby on Rails (RoR), Ruby, JavaScript

Software Engineer

2012 - 2014
  • Developed responsive mobile web applications with AngularJS.
  • Mentored experienced developers who were new to JavaScript.
  • Analyzed front-end technological options (CSS frameworks, Protractor, design patterns, and more) and helped the team settle upon our technology foundation.
  • Led the development of Sears eCoupon application with similar criteria and oversaw its deployment and integration with Sears' subsidiary domains.
Technologies: Java, jQuery, AngularJS, JavaScript


A Chrome developer's tool that generates a diagram on-the-fly for applications running on Statechart.js, see more at It helps developers visualize the state of the application and captures applications' live states.

The noticeable outcome of this project includes:
• New developers can understand the purpose of our framework much quicker.
• Enabled the back-end developers to become better at writing front-end state-related code and understanding the underlying framework.
• Reduced the amount of unit testing that needed to be done for state management.
• Provided a common ground for discussions and planning around state management; this tool became the main visual representation used to analyze options.

Xiang Qi

A complete JavaScript attempt at the popular Song dynasty board game. The pieces and the graphics were rendered using SVG on the React framework. The AI moves were determined by examining and evaluating part or all of the subsequent options and finding the maximum gains around these options.

A simplified version of Shop Your Way mobile coupons application. It has built-in Angular code and is styled mainly in the ShopYour Way proprietary version of Bootstrap.

It provides a list of coupons that have certain categories and availability tagged with them. The user may filter coupons by specifying the criteria (e.g., category). The application was eventually restyled to fit into Sears/Kmart mobile web application. I led a small team of two developers to focus on the user experience distinctions between the tablet and phone.

My main roles in this application include:
• Performant loading and filtering process with the resource APIs which present coupons efficiently to the user.
• Optimized the JavaScript code to achieve a maximum speed between when the data is received and when the coupons are displayed.
• Automated integration with Sears, Kmart, and Shop Your Way.
• Enhanced the end product which included resizing and animating the layout transition from portrait vs landscape view in a pixel-perfect manner.
• Oversaw its delivery and QA feedback.

Official URL:

Official Sears URL (rethemed and restyled for the tablet):

Centro Media Manager

Centro Media Manager is a cloud-based web application platform designed to help create and execute data-driven digital media campaigns.

I handled the development and communication of its inventory management Rails API. I also built the front-end application as well as maintained and designed the APIs that connected our in-house JavaScript frameworks for communication with third-party APIs such as React.

Sears White Label Cart and Checkout

I developed a white-label cart and checkout feature (including many of its payments systems) that was part of a customizable mobile-based online shopping application that we built at Sears; it mainly focused on cross-platform compatibility and dynamic themes by using Angular 1 and Foundation CSS.

You'll need to simulate a mobile device in order to access the app without being redirected.
2008 - 2012

Bachelor of Science Degree in Infromation Systems

SUNY Stony Brook University - Stony Brook, NY, USA


Statechart.js, React, Node.js, TensorFlow, D3.js, Vue, jQuery


Webpack, Jscodeshift, Rollup, Vim Text Editor, Jenkins, Chrome Developer Tools


.NET, AngularJS, Ruby on Rails (RoR), Hyperapp, Electron, React Native, Bootstrap, Redux, Protractor, Express.js, Angular


JavaScript, Ruby, Elm, CSS, Bash Script, TypeScript, Java, Java 6, Scala


Behavior-driven Development (BDD), JavaScript Design Patterns, Functional Programming, Agile


MacOS, Visual Studio Code (VS Code), Linux, Amazon Web Services (AWS), Kubernetes, Docker


PostgreSQL, MySQL, MongoDB, PostGIS


Mobile Web, Front-end Development, Elm Architecture

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