PostHog is looking for a Backend Engineer to join its Feature Flags team. You will be responsible for building and maintaining the high-throughput, low-latency feature flags evaluation engine. The role involves owning this critical service end-to-end, designing, deploying, and scaling systems that respond in single-digit milliseconds and directly impact customer user experience.

What You'll Do

Build and maintain the feature flags evaluation engine that makes complex decisions based on person/group properties at high speed and scale.
Own the entire service from end-to-end: design, build, deploy, and scale the feature flags evaluation engine.
Work on adding new targeting features and continuing to improve the latency of the service.
Make high-level architecture decisions and optimize performance bottlenecks.
Work directly with customers to implement complex targeting rules that meet their specific needs.

What We're Looking For

Experience with any systems programming language and/or backend web frameworks.
Built systems that handle high volumes of requests/data (millions+ per minute).
Ability to choose a sensible architecture quickly and ship it faster than other people think is possible.
Strong understanding of performance optimization techniques, caching strategies, and distributed systems principles.

Nice to Have

Experience with Python and Rust (app is Django, flags API is Rust).
Worked with feature flag systems or similar real-time decision engines.
Actively participated in on-call rotations and have dealt with and resolved production incidents.
Comfortable with provisioning, tuning, and deploying infrastructure.
Worked with benchmarking and profiling tools.
Solid understanding of observability systems and practices.