Machine Learning Engineer

About Citizen

Citizen is the #1 public safety app in the US, used by over 10 million people across 60+ U.S. cities to stay safe and informed in real time. Every piece of information is sourced directly from verified 911 data or live user reports. People have used Citizen to evacuate from fires, recover missing children, and avoid dangerous situations.

We offer three core products:

• Citizen (free): Real-time alerts, live incident maps, and community broadcasts

  Plus ($6/mo): Adds police scanners, crime stats, and customizable alert zones

  Premium ($20/mo): Connects users 24/7 to a trained safety agent who can track them, contact emergency services, and alert loved ones

  Our mission is simple: Protect the World. We're building the first global safety network where people protect each other — instantly and transparently. We've raised $100M+ from Founders Fund, 8VC, Goodwater, and Greycroft, and we're hiring builders who want to work on problems that matter.

About the Role

We are seeking an experienced Machine Learning Engineer to drive the development of critical, 0-to-1 features that bring real-world impact to our users. You will work closely with our operations team to tune and build ML models that process large volumes of radio information – transforming unstructured data into structured, actionable content for our users.

Citizen's information comes from a distributed network of IoT radio devices and as a ML expert you will be responsible for spearheading projects such as:

Real-time audio transcription of highly variable radio data

Association of non-serial information across time

Detecting relevance and filtering noise from critical, potentially life-saving information

Automatically generating structured content from unstructured audio/text streams

You’ll also guide prioritization and impact analysis across ML initiatives, help identify opportunities to leverage emerging AI/ML tooling, and ensure that our models scale reliably as we grow. If you’re a proactive and innovative individual with a passion for impactful machine learning and a track record of delivering production-grade solutions, we invite you to join us and shape the future of Citizen.

Our Challenges

• Scaling: We have one of the fastest-growing organic user bases in key metropolitan areas, and have expanded to multiple other cities. We are focused on scaling to a nationwide launch both technically and operationally.

  Bursting: We designed our infrastructure to scale without notice in case of a spontaneous event where we need to inform our entire user base. On significant events, we see hundreds of thousands of 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 police, fire, and medical audio every day to identify incidents that impact our users’ safety. Building robust ML models for audio analysis, event matching, and structured content creation at scale is a key priority.

  Our Stack - languages and technologies we use and teach

  Services: Go for transactional systems; Python for analytical and ML systems

  Datastores: Cassandra, MySQL, Redis, Google PubSub

  Infrastructure: Kubernetes on Google Cloud; heavy utilization of OpenAI (GPT and Whisper) products with a growing base of internal ML infrastructure

Preferred Qualifications

• Computer Science degree or Machine Learning-related degree; or equivalent work experience in the field

  Strong theoretical grounding in core Machine Learning concepts and techniques

  Experience with a variety of ML techniques and frameworks, e.g. data discretization, normalization, sampling, linear regression, decision trees, SVMs, deep neural networks, etc

  5+ years experience leading and delivering effective ML solutions for production use cases

  Bonus: experience with ML for audio or natural language data, and integrating ML pipelines with human-in-the-loop systems

Salary Range

This role offers a base salary of $220,000 - $220,000 per year, plus equity.

Compensation & Benefits
We offer competitive salary, equity, and a full benefits package, including:

100% employer-paid medical, dental, and vision for employees