Scroll To View More
Leonardo Kim, Software Developer in Nassau, NY, United States
Leonardo Kim

Software Developer in Nassau, NY, United States

Member since February 19, 2019
With a bachelor's degree in computer science from NYU, Leonardo has spent over the past decade building robust web apps. Nowadays, he builds single-page applications using React, Redux, Angular, Vue.js, Ext JS, D3.js, Material-UI, Semantic UI, Ant Design, Bootstrap, Node.js, Ruby on Rails, and so on. He's also worked on Firebase platform. Leonardo joined Toptal to find longterm projects that involve React, Angular, and Node.js.
Leonardo is now available for hire



  • JavaScript, 10 years
  • React, 5 years
  • Node.js, 5 years
  • Vue.js, 5 years
  • AngularJS, 5 years
  • Ruby on Rails (RoR), 4 years
  • React Native, 4 years
  • Angular, 3 years
Nassau, NY, United States



Preferred Environment

macOS, iTerm 2, Git, Slack, VS Code

The most amazing...

...thing I've coded is a team communication application built with React and Electron.


  • Senior Full-stack Web Developer

    2013 - PRESENT
    • Developed rich UI/UX applications using React, React Native, Redux, Redux-saga, Angular, Vue, Ext JS, D3.js, Ant-Design, Material UI, Semantic UI, Bootstrap, jQuery, and DHTMLX.
    • Built many RESTful API endpoints using Node.js/Express.js, Rails, Laravel, Go, and Scala.
    • Integrated many third-party APIs such as AWS S3, Twilio, Smooch, LOB, Stripe, Facebook, LinkedIn, Twitter, Google+, Google Map, Geocode, and so on.
    • Worked with AWS Lambda and Serverless frameworks.
    • Designed and implemented database models and drivers using MongoDB, MySQL, PostgreSQL, and Microsoft SQL.
    • Worked on hosting web applications using AWS ELB, EC2, and CloudFront.
    • Integrated Socket.IO and Firebase to applications to provide real-time communication.
    • Used Git, SVN, and CVS.
    Technologies: React, React Native, Redux, Redux-saga, Angular, Vue.js, Node.js, Express.js, Ruby on Rails, Laravel, WordPress
  • React Native Developer

    2019 - 2019
    Launch Interactive, LLC (via Toptal)
    • Created a meal-ordering app using React Native, and React-Apollo.
    • Used Agile development methodology.
    • Utilized GraphQL.
    • Used a React Native navigation package for navigation of the app.
    • Built the app with well-structured code.
    Technologies: React Native, React-Apollo
  • Front-end Web Developer

    2009 - 2013
    • Developed an internal employee schedule, shift, and slot management application for the company.
    • Heavily used the DHTMLX library on the UI.
    • Implemented page designs in standard-compliant dynamic XHTML and CSS.
    • Developed a task management application like Trello.
    • Built a rich UI/UX using jQuery and jQuery-UI libraries.
    • Maintained reusable components and modules.
    Technologies: DHTMLX, jQuery, PHP


  • Team-communication Application (Development)

    Here, I developed a real-time team communication app.

    • Worked on React, Redux, and Redux-saga with Ant Design components.
    • Built a Node.js/Express.js back-end RESTful APIs along with a Passport.js authentication package.
    • Designed MongoDB data models and utilized a Mongoose ORM.
    • Integrated Socket.IO to provide real-time communication.

    Technologies: React, Electron, Node.js

  • Language-learning App (Development)

    I built a language-learning app for Arabic learners.

    • Built an authentication system and user management and learning class management modules using Angular.
    • Integrated the AngularUI and Bootstrap libraries.
    • Built a Ruby on Rails back-end providing RESTful APIs.
    • Integrated third-party APIs such as Facebook, Google+, and Twitter.
    • Implemented internationalization and localization.

    Technologies: Angular, Ruby on Rails

  • Audio Player (Development)

    Here, I developed an audio player app and Node.js back-end to play music and podcasts with playlists, artists, and favorite lists.

    • Worked on React Native front-end integrating Node back-end.
    • Developed Node.js/Express.js back-end, designed and implemented MongoDB models and schemas.
    • Used GraphQL.
    * Used Firebase.

    Technologies: React, React Native, GraphQL, Node.js, Firebase

  • Automation Platform for Asset Discovery and Service Mapping using React (Development)

    Here, I developed the cloud-based digital enterprise management solution that automates asset discovery and service mapping.

    • Initially built it with Angular and Material 2 UI.
    • Refactored the UI to migrate it from Angular to React.
    • Built a front-end with React, Redux, and Redux-saga along with an Ant Design library.
    • Used D3.js to draw graphical charts.

    Technologies: React, Angular, Redux, Redux-saga, Ant Design, D3.js

  • Airline Scheduling Application (Development)

    I developed an airline application for the management of flights, slots, and schedules.

    • Customized an airport management module on the Express.js back-end based on the new requirements.
    • Updated the flights' arrangement UI using Ext JS.
    • Updated an authentication system to use JSON web tokens.
    • Improved the slots and schedules data operation performance by updating database table indexes and definitions and by creating stored procedures.

    Technologies: Ext JS, Node.js

  • Employee Schedule and Shift Management Application (Development)

    I developed an employee schedule and shift management application.

    • Built a scheduling UI using the jQuery Full Calendar library and vanilla JavaScript.
    • Refactored the UI to use Angular and Bootstrap UI.
    • Improved UI performance by reducing unnecessary modules.

    Technologies: AngularJS, jQuery, Bootstrap UI

  • eCommerce Shop (Development)

    I've also developed an eCommerce shop.

    • Built Angular and Bootstrap components providing a rich UI/UX.
    • Constructed RESTul APIs using Node.js/Express.js and MongoDB.
    • Integrated Stripe APIs for payment processing.
    • Integrated Twilio APIs for mobile SMS messaging.

    Technologies: Angular, Node.js, Stripe, Twilio

  • Social App that Posts Texts, Images, and Videos (Development)

    Here, I developed a social app that posts media content.

    • Updated a media content management module using React, Redux, and Redux-saga on the front-end.
    • Created a media conversion module for content uploaded on an Express.js-based back-end.
    • Integrated AWS S3 bucket APIs and social APIs.
    * Used Firebase.

    Technologies: React, Node.js, Firebase


  • Languages

    JavaScript, TypeScript, ES7, Ruby, GraphQL, PHP, HTML, CSS, Less, Sass, SQL, ECMAScript (ES6), Java, Scala, Golang
  • Frameworks

    Redux, Angular, Ant Design, Material-UI, Bootstrap 4, Ext JS, Express.js, Loopback, Sails.js, Laravel, Ruby on Rails (RoR), Jest, React Native, Ionic, Serverless Framework, Flux, Angular Material, AngularJS, Spring, Electron
  • Libraries/APIs

    React, Redux-saga, Node.js, Twilio API, Facebook API, LinkedIn API, Twitter API, Google+ API, Stripe, D3.js, Highcharts, Vue.js, Socket.IO, Vue Material, React Router, React Redux, Redux Form, Formik, MobX, RxJS
  • Tools

    Amazon Virtual Private Cloud (VPC), Grunt, Gulp.js, Webpack, Yeoman, Angular CLI, Mocha, Karma, AWS SDK, VS Code, Redux Thunk, Auth0, Git
  • Paradigms

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

    Meteor, MacOS, Linux, Unix, AWS Lambda, Firebase, Ubuntu
  • Storage

    MongoDB, MySQL, PostgreSQL, Microsoft SQL Server, AWS DynamoDB, AWS RDS, Redis
  • Other

    Semantic UI, AWS API Gateway, Axios, Apollo, ESLint, TSLint, Vue-router


  • Bachelor's degree in Computer Engineering
    2005 - 2009
    New York University - New York, NY, USA
I really like this profile
Share it with others