QuizUp is a mobile trivia game, which reached over 80 million users across the world, peaking at 1.2M daily active users.
I wrote the initial implementation of an A/B testing service which allowed QuizUp to run feature experiments. As a side-effect this service alleviated the stress of shipping the mobile clients by making it possible to slowly roll out features and rolling back if we discovered bugs without submitting another binary version.
Storage optimisation: Optimized how QuizUp stores information on questions players have seen (essential for picking questions). This optimization reduced a 7TB dataset to 300GB without loosing precision or functionality.
Player search: Built a service for search using ElasticSearch that searches for players most relevant to you, using friends, mutual friends, and ranks strangers that have mutual interests with you as more relevant.
On-call: I was part of a weekly on-call rotation at QuizUp. If anything critical happened to our systems off-hours, the on-call person will respond and fix if possible, otherwise call the service owner and follow through with fixes and post-mortems.
Game service: Worked on refactoring and rewriting the game flow in the backend system of QuizUp, with the goal of handling the scale of 2M concurrent users.