At HackerEarth we recently launched FaceCode - a remote interview platform with pair programming, facetime, multi-room chat, and activity log features. To build a scalable and reliable platform, supporting all these real-time features, we used Firebase to a much extent. The talk will start with a live demo of FaceCode - the remote interview platform. It will be followed by a brief introduction to Firebase and its applications. Moving forward we will dive deep into the macro-architecture and the implementations of pair programming, video call state, user presence management, and other real-time features in FaceCode build using Firebase. At last, we will learn Operational Transformation technology and Firebase transactions which played a key role in consistency control and conflict resolution for the collaborative features like pair programming. Slides: goo.gl/d66YvY