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HackerRank personalizes coding interviews with video and real-time collaboration

Using Twilio Video and WebRTC, HackerRank built a next generation developer interviewing platform.

The Results
Companies use HackerRank's interviewing platform
Programming languages can be validated in real time
Weeks to integrate Twilio Video into the HackerRank platform

Back in 2012, HackerRank set out to build a world class developer recruiting platform. To do so, HackerRank needed to focus on developing innovative interviewing features, like instant code validation in 30 languages while evaluating the interviewee’s ability to communicate their thought process. Twilio manages their communications so HackerRank can focus on shipping and iterating on new features for its customers.

HackerRank humanizes developer interviews by allowing interviewers to see code as it is being written with CodePair and ask candidates to delve into their thought process. The HackerRank platform does this by enabling participants to share code and connect via video in real-time. More than 1,000 companies, like VMware, Red Hat and Cisco use HackerRank’s real-time video evaluation tool to build top-notch engineering teams. The HackerRank platform enables hundreds of thousands of engineers around the world to interview for positions by showcasing their coding skills through coding challenges rather than resumes.

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In order to build a high quality and scalable platform, HackerRank needed to make the process of connecting candidates with interviewers as seamless as possible. HackerRank’s first requirement was being able to provide a reliable virtual interview experience. HackerRank used real-time voice and video chat to make the interview as human as natural as possible, by letting interviewers and candidates collaborate and validate code in more than 30 programming languages.

HackerRank first added video to their application using with a different video provider, but as they scaled their product both to new geographies and enterprise clients, they found that the could not reliably establish or maintain video connections. HackerRank’s early video efforts would not work consistently, particularly for clients behind stringent enterprise firewalls. When live video chat & coding streaming wouldn’t work, users would have to resort to an out of app communications experience like Skype or Google Hangouts. Forcing recruiters and interviewers out of the platform was not only a bad user experience, but they lost the ability to collaborate on coding challenges and validate them in real-time. HackerRank needed to quickly find a way to reliably connect recruiters and candidates in a wide range of network conditions and firewall restrictions.

The Twilio team is world class in building reliable, secure and scalable communication tools for developers.

Harishankaran Karunanidhi, Co-Founder & CTO, HackerRank

Connecting globally, reliably

While video reliability suffered and customers complained, HackerRank explored building out their own video platform. However, they realized that building and maintaining their own signaling solution to establish video calls and globally deploying media servers for relaying calls around firewalls would require significant upfront investment and be even more expensive to operate. Ultimately HackerRank decided that operating reliable real-time video was not core to their business. Instead, they turned to Twilio which they were already using to power their voice calls.

Twilio’s Programmable Video included highly reliable TURN server to relay the media around corporate firewall and support transport through even the most stringent networks. This allows participants to connect even if their network won’t allow UDP connections, by supporting UDP tunneling through TCP. And where networks restrict which ports can be used, Video can make use of port 443, typically used for HTTPS traffic. Twilio's security & reliability drove HackerRank's decision to tightly integrate Twilio into their existing product and continue to use Twilio for additional functionality. “Twilio’s ultra-reliable communications platform is why we love Twilio and is the main reason we chose them as our solution provider in the first place,” says Harishankaran Karunanidhi, Co-founder & CTO, HackerRank. Adding video with Twilio enabled HackerRank to continue using a common library, and receive the same high quality and highly responsive customer support.

Twilio’s API is very simple and makes it easy to add additional features and ship them quickly.

Abhishek Gahlot, Software Engineer. HackerRank

To get started, HackerRank cloned a Twilio GitHub repo which helped them build a proof of concept in 2-3 days. HackerRank then added the Video SDKs into their product to create the video interview experience they wanted alongside the live coding tool they had built. “Twilio’s API is very simple and makes it easy to add additional features and ship them quickly,” says Abhishek Gahlot, Software Engineer at HackerRank. The Twilio JavaScript SDK easily integrated into HackerRank’s existing platform and allowed them the flexibility to integrate with different platforms down the road.

The entire integration process for adding Twilio Programmable Video to the HackerRank platform took about 3 weeks. Twilio Video had “all the great qualities we’d come to expect from a Twilio product” said Abhishek Gahlot, Software Engineer at HackerRank. Being able to embed video directly into their product enabled HackerRank to provide enormous value to users by incorporating video conferencing alongside video challenges. This live coding allows recruiters to better understand interviewees’ thought process and ask questions in real-time. The speed and extensibility of HackerRank’s video product wouldn’t have been possible with a traditional packaged solution.

You’re hired!

Now, participants in HackerRank’s interview platform receive a screen pop that instantly connects them via video. Using Twilio Video, video quality has significantly improved and HackerRank’s customers have experienced no disconnection issues. These improvements have positively impacted HackerRank’s bottom line by making the developer user experience on the platform better. Additionally, since most of HackerRank’s customers are in the US and India, and Twilio’s global platform makes it easy to accommodate customers in any location.

Check out these JavaScript, iOS, and Android Quickstarts to see how HackerRank learned to build with Twilio Video.