Jai Ko, Developer in Walnut Creek, CA, United States
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Jai Ko

Verified Expert  in Engineering

Software Developer

Walnut Creek, CA, United States
Toptal Member Since
March 1, 2019

Jai is a skilled front-end developer with expertise in jQuery, Vue, and React, among other front-end technology. He played an instrumental role in the operation of Steps Education, increasing its revenue by 250%+ over the course of three years. At his most recent role at Pilot.com, he created the dashboard, employee time tracker, and the customer portal, which helped employee efficiency, analytics, insights, and communications.


CSS, TypeScript, React, React Native, JavaScript, Test-driven Development (TDD)...
CSS, React, Flow, Hack, GraphQL, JavaScript, Test-driven Development (TDD), Git...
Amazon Web Services (AWS)
CSS, HTML, React, TypeScript, CI/CD Pipelines, JavaScript...




Preferred Environment

Visual Studio Code (VS Code), MacOS, Windows

The most amazing...

...app I've created solves the KenKen puzzle, which is like sudoku, but with math.

Work Experience

Senior Software Engineer

2022 - 2023
  • Implemented features and fixed bugs on web and mobile, while growing and educating junior members of the team.
  • Launched a campaign to train other engineers on the correct way of implementing i18n.
  • Rearchitected and improved type across mobile and web to significantly reduce bugs and enhance readability, testability, and portability.
Technologies: CSS, TypeScript, React, React Native, JavaScript, Test-driven Development (TDD), Git, HTML

Software Engineer (Web3 Services)

2021 - 2022
  • Built the necessary tools as the company transitions from Web 2 to Web3.
  • Created an internal tool similar to OpenSea.io that enabled users to view information on NFT and blockchain addresses.
  • Actively engaged with a wide range of teams to scope out their needs and prioritize features that had the largest impact on the business.
  • Wrote GraphQL queries that enabled searching for NFTs by different attributes.
  • Rearchitected the internal tool as more teams added features and tools to it.
  • Taught and guided interns through their technical and career journey.
Technologies: CSS, React, Flow, Hack, GraphQL, JavaScript, Test-driven Development (TDD), Git, PHP 5, HTML

Software Engineer

2020 - 2021
Amazon Web Services (AWS)
  • Developed the console and the infrastructure behind it for the elastic load balancing org.
  • Rebuilt the console written in GWT with an internally developed React component library.
  • Used RxJS and Redux to manage the internal state of the app and to communicate with the back end.
  • Wrote and maintained end-to-end (E2E) tests as well as component tests.
  • Responded to inquiries and requests from both internal and external customers, including emergencies.
  • Monitored and maintained the CI/CD pipeline for smooth and bug-free worldwide deployment.
  • Wrote and improved various internal docs that reduced onboarding time from 6 weeks to 1 week.
Technologies: CSS, HTML, React, TypeScript, CI/CD Pipelines, JavaScript, Test-driven Development (TDD), Git, RxJS

Front-end Developer

2019 - 2019
  • Developed and tested pixel-perfect UI based on a provided design.
  • Communicated with stakeholders such as designers and product specialists to improve the existing UI and initiate new projects.
  • Set precedents in coding styles, discussion practice, and other elements of company-wide engineering culture.
  • Communicated with back-end engineers to spec out front-end needs.
  • Recreated the dashboard page that displays thousands of customer statuses with details about their work completion, assignee, and other information.
  • Made asynchronous calls to a REST API via JavaScript Promise to update pages.
  • Optimized the pre-existing codebase by modernizing it with the newest standard of HTML/JavaScript/CSS and adding greater test coverage.
  • Documented progress, accomplishments, and technical specs for added features and debugging.
  • Addressed bugs and comments with short turnarounds.
Technologies: Git, PostgreSQL, NPM, Vue Router, Vuex, Vue CLI, Vue, JavaScript, CSS, HTML

Front-end Developer

2019 - 2019
  • Helped make an engaging and informative web page using Vue and its ecosystem.
  • Built a user and admin dashboard as a single-page application.
  • Connected the front-end and the "Wire", a propriety back-end interface created by the back-end team to serve the browser extension, web app, and native app.
  • Worked with the design/UI team to implement beautiful and functional apps expediently.
  • Configured webpack, Vue CLI, and Babel to serve our needs.
Technologies: Vue Router, Vuex, Vue CLI, Vue, JavaScript, CSS, HTML

Founder | Full-stack Developer

2015 - 2017
Steps Education
  • Created the front end to lazy load various math app plugins using jQuery Ajax functions.
  • Implemented a performance tracking system to measure students' active time, assignment completion, and comprehension using JavaScript.
  • Stored, retrieved, and analyzed various user metrics with PHP and MySQL.
  • Designed UI/UX from the ground up and implemented it using HTML, CSS, JavaScript, and jQuery.
  • Planned, designed, and implemented various math apps to help students understand math, which could then be plugged into the platform.
Technologies: MySQL, PHP, jQuery, JavaScript, CSS, Vue, HTML


MathTestNinja was created as a demonstration of Jai's capability to make a fully functioning web application from the ground up using a modern tech stack, which in this case is Vue, Vuex, Vue Router, Firebase Hosting, and Firebase Authentication.
2005 - 2011

Bachelor of Science Degree in Mathematics

University of Washington - Seattle, WA


React, Vue, Vuex, Vue 2, jQuery, RxJS


NPM, Vue CLI, Git, Flow


CSS, JavaScript, HTML, PHP, PHP 5, TypeScript, Hack, GraphQL


React Native


Object-oriented Programming (OOP), Functional Programming, Test-driven Development (TDD)


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


PostgreSQL, MySQL


Vue Router, CI/CD Pipelines, Firebase Hosting

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