Senior Fullstack Engineer (Moderation)

About Stream Stream powers real-time Chat , Video , Activity Feeds , and AI Moderation for more than 1 billion end users across 4,000+ apps, from Strava and Bumble to eBay and Patreon. Our platform processes billions of API requests per month and supports applications with millions of concurrent users, while delivering highly reliable, low-latency services and a great developer experience. The role We're looking for a Senior Full Stack Engineer I to join Stream on our mission of elevating the quality of apps for billions of users globally. You'll own the backend of our AI Moderation product: building new capabilities and making the Go services behind them cleaner, faster and more reliable. This is a full-time role, hybrid with 3 days a week in our Toronto co-working space. What you'll work on You'll join our five-person Moderation team, which builds the product customers use to detect, review and act on harmful content in their apps. The role leans backend. Dedicated frontend engineers own the moderation dashboards, and you'll own the Go services, data model and integrations behind them, stepping into React when a feature spans the stack. You'll work closely with the team lead, our other Toronto-based engineer, Infrastructure, and the Customer Success and Support teams, and directly with customers' trust and safety and engineering teams. Here's the honest current state: the product has grown fast and the backend has grown with it. There's real cleanup, refactoring and simplification to do, and you'll have the room to do it well. You'll also give the team coverage in North American hours, which today rests largely on one engineer. Job responsibilities: Build new moderation features: design and ship Go services from database schema and API endpoints through to production rollout, including work on our new AI moderation flow. Clean up the backend: refactor existing moderation services, reduce technical debt, simplify code paths and raise test coverage. Improve reliability and performance: strengthen alerting and observability, and fix scaling and latency issues in the moderation pipeline. Own third-party integrations: maintain and extend the AI and moderation providers that plug into the pipeline. Keep production healthy: diagnose defects to root cause and take part in on-call, with a focus on North American hours. Work with customers: troubleshoot their issues directly and bring what you learn back into the roadmap. Work across the stack when needed: ship React changes alongside the frontend engineers and review your peers' code. About you You're a backend engineer at heart who is comfortable picking up frontend work when a feature needs it. You enjoy leaving a codebase better than you found it, and you'd rather simplify a service than add another layer to it. You like owning problems end to end, including the ones that show up in production or in a customer conversation. You probably won't enjoy this role if you want a pure frontend position, a large team with a fixed process, or a job with no on-call. The team is small, the product is moving fast, and North American coverage is part of the job. You have: 3+ years of professional software engineering experience, mostly on the backend. Solid backend experience in Go, Python or a comparable language, and willingness to work in Go. We run a 10-week internal Go onboarding programme. Experience designing REST APIs and relational data models (ideally Postgres), and working with Redis. A track record of shipping features used at scale and of refactoring and improving existing production systems. Working knowledge of React and TypeScript or JavaScript. Experience with automated testing across client and server code. Comfort working with customers and handling production incidents. Bonus points: Exposure to trust and safety, content moderation or policy enforcement products. Professional experience with Go. Experience with GCP or another major cloud provider. Experience integrating LLM or ML-based services into production systems. Message queue experience. Full-text search experience. Open-source contributions. What makes this role exciting Scope: you'll own the backend of a product area, with the room to clean up and reshape it. Impact: AI Moderation is one of Stream's growth products, and you'll help ship its new AI moderation flow and the features that come after it. Stack: Go, Postgres, Redis and React on GCP, with Claude, Cursor and ChatGPT Codex as everyday tools. Starting point: a small team where your work is visible from week one, and a second Toronto engineer to work with closely. Why join Stream? We're a Series B company with offices in Boulder, Amsterdam, Skopje and Toronto, and a team of 140+ people from 37 nationalities. We're backed by Felicis Ventures, GGV Capital, 01 Advisors, Techstars, and Arthur Ventures, with angels including Dick Costolo (ex-CEO of Twitter), Olivier Pomel (CEO of Datadog), Tom Preston-Werner (co-founder of GitHub), and Nicolas D