About Citizen

Citizen is a free app that keeps you and your loved ones safe. It is a powerful force for good that has already evacuated people from burning buildings, diverted school buses from nearby terrorist attacks and reunited missing children with their parents. 

Using our unique technology, 911 alerts are made available to the public and are accompanied by live stories, real-time updates, and user-generated content to provide you with the information you need to protect yourself and your loved ones. We act fast, break news, and give people the immediate information they need to stay safe. And we’re just getting started. 

This year Citizen will expand further across the United States with the express mission of making your world a safer place. We’re looking for passionate, mission-driven individuals to help take the Citizen app to the next level as we scale up nationwide. With a group of passionate builders from Facebook, Square, Uber, Google and HQ Trivia, Citizen is the company your current company doesn’t want you to know about.

Our Challenges

• Scaling: We have one of the fastest-growing organic user bases in NYC, and have expanded to multiple other cities. We are focused on the nationwide launch and the need to support that scale. A Citizen international launch will follow.
• Bursting: We designed our infrastructure to scale without notice in case of a spontaneous incident where we need to inform our entire user base. On significant events, we see over a million simultaneously connected clients and their associated live streams. The core systems need to be able to efficiently support these traffic patterns and continue to scale to millions of more users in the future.
• Machine learning: We process thousands of hours of audio every day looking for incidents that impact our users’ safety. To do this at scale, we’ve built ML models for audio analysis and targeting using the current state of the art from academia.
• Analytics: We want to alert users to the incidents that matter to them, in a way that scales across different geographic densities and demographics.
• Mobile video streaming: Our app will ingest high-quality video at low-latency, transcode, and redistribute the video to external media outlets seamlessly.
• Radio hardware: We build our own software-defined radio-based devices to consume all radio dispatch in every major city, whether analog or digital.

Our Stack - languages and technologies we use and teach

• Mobile: Swift (iOS), Kotlin (Android)
• Web: React.js, TypeScript
• Services: Go for transactional systems; Python for analytical systems
• Datastores: Cassandra, MySQL, Redis, Google PubSub
• Infrastructure: Kubernetes on Google Cloud