Senior Backend Engineer (FastAPI)

About us

comm1t is a specialist IT recruitment agency delivering top engineers across Poland and Europe 🇪🇺. We combine experienced recruiters with autonomous AI agents and an obsessive focus on quality — sourcing 24/7 across LinkedIn, GitHub, and beyond to reach engineers who aren't actively job hunting but are open to the right move.

We don't flood you with CVs. We get to know each candidate's skills, values, and goals, then send only the best-matched people — and we stay close through onboarding and the first months to make sure the placement lasts.

About the role

You'll lead the backend that drives the AI features — the APIs, the data pipelines, and the orchestration that connects the product to the language models doing the actual work. In practice that's querying across large document sets, getting trustworthy answers out of LLMs and their tool calls, pushing results to the UI as they stream, and grinding through lengthy background jobs without the whole thing toppling over.

Forget CRUD. The real difficulty is making AI systems fast and reliable on confidential data, at production scale. The architecture choices land on you early, and you'll be the one living with them.

What you'll do

• Architect and ship the APIs and services that everything else depends on

• Own the AI plumbing end to end: retrieval, orchestration, tool-calling, streaming, and the evals that tell you whether the results are worth anything

• Make async and distributed workloads rock-solid — document ingestion, embeddings, and long jobs running on Redis

• Wire up integrations with what clients already use (email, document stores) and harden them for real-world traffic

• Put data security and isolation front and center, because clients are handing over material they can't afford to leak

Who you are

• Seven years or more delivering production backends — though how deep you go matters more to us than the figure itself

• You think in failure modes, not just the happy path

• You've shipped genuine LLM systems (RAG, tool-calling, agents), or you can't wait to — and you've got a feel for where they fall apart

• You lean on AI coding tools (Claude Code, Cursor, Copilot) and get real value from them: more speed, yes, but you grasp and back every line — code you'd reject in someone else's review is code you won't merge in your own

• A startup that keeps changing course doesn't faze you — plans get set, then torn up and redrawn

Tech stack experience

• Python: 6+ years

• FastAPI: 3+ years

• PostgreSQL / SQL

• Redis: 2+ years

Nice to have

• RAG or vector search experience

• LangChain or LlamaIndex

Tech stack

• Python
• fastapi
• Redis
• Celery
• RabbitMQ
• PostgreSQL
• Langchain
• RAG