Principal Software Engineer
January 2014 - Present

Duolingo is the most popular way to learn a language online and was named App of the Year by Apple.

I wrote the flagship apps for web and Windows, the DET web app, the API backend… and even the Pittsburgh airport's wifi login page. I've also led our Android, internal tooling, and open source efforts with a focus on code quality and developer productivity.


Member of Technical Staff
April 2017 - June 2017

OpenAI is a research lab founded by Elon Musk and Sam Altman in 2015 with the goal of creating safe, human-level artificial intelligence.

I worked on the infrastructure team, developing internal tools and managing our clusters.


December 2017

Chronofile is a personal time tracking app that I created to record and analyze the time, duration, and geographical location of my daily activities. I've been logging events at the pace of about 20 per day since 2017.


December 2015

Triviality is a free online game that I designed and coded in order to learn React.

Inspired by Classic Trivia and What's the Lyric, Triviality is a question-and-answer quiz app that pulls data from the J! Archive via jService. It's optimized for the Amazon Fire TV but also works with keyboard, mouse, and/or touchscreen.

Duolingo Earth

December 2015

For the 2015 company hackathon, coworker Karin Tsai and I created a WebGL map that visualizes global user activity in realtime. Come visit Duolingo HQ and you'll see it on display in the lobby.

Face-Recognizing Page Turner

April 2015

I got tired of fiddling with the mouse while practicing guitar at the computer, so I shamelessly shoved years of computer vision research into an automation script. More details here.

Jeopardy! Simulator

December 2014

True Daily Double is a free multiplayer online game that I designed and coded in order to learn Angular.

It recreates the Jeopardy! game show experience for up to six players using clues from the J! Archive. Real-time interactivity is achieved in pure JavaScript using WebSockets.

CIFEr Hedge Fund Competition

September 2013 - February 2014

I put together a mock trading webapp that hosted a 40-day educational contest featured in the IEEE's Computational Intelligence for Financial Engineering & Economics conference in London. The results were published at WSC '14.

Epic Systems

Research and Development Intern
May 2013 - August 2013

I worked on improving the diagnosis lookup interface, which involved a lot of plain old JavaScript (no external libraries allowed!), some C#, and usability testing with local physicians.


August 2007 - Present

Online Tools

Open Source

See my GitHub profile for more side projects.


Lead Developer
October 2012 - December 2013

Ticketmelon is a ticket sales and event promotion app based in Bangkok, Thailand. A few high school classmates, my college roommate, and I worked on the initial version.

Stock Market Simulation

September 2012 - September 2013

A friend and I wrote a stock market simulator and visualizer for the University of Virginia's Financial Decision Engineering Research Group. The results were published at WSC '14.

3D Neuron Modeler

October 2011

My neuroscience research experience lasted for just a few days, but during that time I came across some test data that proved suitable for trying out WebGL months later.

Here's a demo. There are almost 6000 shapes, so it may take a few seconds after you load the data before anything appears.

Raytracing, Morphing, and OpenGL

August 2012 - December 2012

Very significant portions of my allotted time in this world were spent on CS 4810: Intro to Graphics. A particularly inordinate number of hours was spent on the second project. The results were definitely worth it.


2004 - Present

After six years of playing clarinet in a sitting band, I joined UVa's marching band for fun and profit - willingness to run around carrying a 30-pound sousaphone has its perks.

Nowadays I mostly stick to guitalele and piano. Check out my face-recognizing page turner if you're a Linux musician.


July 2010 - Present

The styles and scripts are handcoded in Sublime Text and stitched together with Jekyll and Sass.

More details and source code.

Calculator Programs

August 2007 - December 2013

The TI-84 graphing calculator required for my math analysis class gave me my first taste of coding.

I still have and use the same calculator for my programs, which range from games like Blackjack and Simon (9th grade) to binomial tree option pricers (last semester of college).

DuolingoChronofileOpenAITrivialityTrue Daily DoubleCIFErJinSup3D Neuron ModelerOpenCV Page TurnerEpicGitHubTicketmelonGraphicsSousaphonechaidarun.comCalculator Programs