Backend Engineer, Infrastructure

36 Labs is a seed-stage startup that started out of the UCL Machine Learning lab. We bootstrapped to 10 people, and now we're on the next leg of growth.

AI can generate almost any media, but it still can't judge what wins human attention. AI-generated content on social platforms is growing fast, and we think every creative workflow will be agent-assisted or fully agentic within a few years. Our work is improving how models reason about creative decisions, learning from how real audiences respond to the content we make.

You'll own our core platform: deployment, service communication, job orchestration, and the APIs and database that our products depend on as we scale throughput 100x over the next year.

You'll have the autonomy to shape the platform's infrastructure, with scope to grow into technical leadership. You'll work closely with the CTO on architecture, with machine learning engineers to develop and implement our "creative harness", and with content engineers to improve its capabilities.

• Design system architecture: service boundaries, data and API contracts, and service-to-service communication.
• Lead the migration from Railway to Cloudflare: target architecture, migration plan, cutover and decommissioning, with no disruption to production workloads.
• Own deployments and production health across our services: CI/CD, environments, rollbacks, secrets, observability and feature flags, fixing issues at the cause and turning them into alerts, runbooks and better defaults.
• Own the scheduler, queues and sandboxes behind our long-running, multi-step work, building recovery, end-to-end traceability, and cost and latency efficiency.
• Build reliable, well-documented internal APIs: simple, durable primitives that the rest of the team, downstream products and our agents build on top of.
• Own our data platform, including schema design, migrations and performance at scale.
• Set the standard for backend engineering and own the vision for our software factory: design and code quality, documentation, and the guardrails that enable the team to ship high-quality code at speed.

• BSc in Computer Science, Engineering, Mathematics, Statistics, or the equivalent in the form of experience. Experience writing production Python and Type Script.
• 4+ years building and running backend systems in production, including how they were deployed and operated.
• Strong experience building job and workflow systems in production, with sound judgment on idempotency, retries and back-off, concurrency and parallelism.
• Strong experience running Postgres in production, including schema design, migrations on live data and query performance.
• Built infrastructure from scratch, scaled it through rapid growth in load, and led at least one significant platform migration.
• Owned infrastructure end to end: containers, CI/CD, networking, observability, incidents.
• Led technical work: set direction, reviewed designs, mentored.
• Taken complex systems from ambiguous problem statements to reliable production services, including APIs that remained reliable as load and consumers grew.
• Systems or projects you've built and can discuss in technical depth.

• Used Cloudflare in production:
  Workers, Queues, Workflows, Durable Objects, R2 or Containers.
• Founding or early engineer at a startup, or equivalent ownership inside a larger company.

Python (FastAPI, SQL Alchemy, Alembic), Type Script, Postgres, a Postgres-backed job queue, Docker, Git Hub Actions, Sentry, LLM and generative media APIs.