Senior FastAPI Developer

Newcode.ai; Warszawa; On-site; PLN 120,000 - 150,000; Full time

Benefits offered by this job

Driver of innovation

Collaborative team environment

Flexible work culture

Job summary

Newcode.ai in Warsaw, Poland, is looking for a skilled backend developer to lead API and service design for AI tools in legal and professional services. The ideal candidate possesses at least seven years of experience in backend systems, familiarity with AI coding tools, and a deep understanding of data security.

Join a dynamic and innovative team where you will contribute to building production-scale AI systems while navigating an exciting startup environment with a flexible, English-speaking culture.

Qualifications

• At least seven years building backend systems that run in production.
• Experience with real LLM-powered systems or knowledge of potential failures.
• Familiarity with AI coding tools like Claude Code, Cursor, and Copilot.

Responsibilities

• Design and build the APIs and services for the products.
• Develop the AI plumbing including retrieval and orchestration.
• Ensure reliability of async and distributed work.
• Integrate with existing client systems efficiently.
• Maintain high data security standards.

Skills

Backend system building

AI system integration

Data security

Using AI coding tools

Tools

Python

FastAPI

PostgreSQL/SQL

Redis

Job description

Who are we?

We build AI tools for firms in legal and professional services: software people use for real work, not demos. We started a few months ago and already have paying clients who rely on what we ship. The team is small and moving fast.

The role

You'll own the backend behind our AI features. That's the APIs, the data pipelines, and the orchestration sitting between our product and the language models doing the work. In practice it means running retrieval over large sets of documents, getting dependable results out of LLMs and their tool calls, streaming responses to the UI, and processing long jobs in the background without things falling over. It isn't CRUD work. The hard parts here are keeping AI systems accurate and fast with confidential data, at production scale. You'll make architecture calls early and live with them.

What You'll Do

• Designing and building the APIs and services our products run on.
• Working on the AI plumbing: retrieval, orchestration, tool-calling, response streaming, and the evals that tell us whether the output is any good.
• Keeping async and distributed work reliable: document ingestion, embeddings, and long-running jobs on Redis.
• Building integrations with the systems clients already use, like email and document stores, and making them hold up under load.
• Taking data security and isolation seriously, since clients hand us confidential material.

Who You Are

• At least seven years building backend systems that run in production. Depth matters more to us than the number.
• You think about how things fail, not just how they behave when everything's fine.
• You've built real LLM-powered systems, or you're itching to: RAG, tool-calling, agents. You know where they tend to break.
• You use AI coding tools (Claude Code, Cursor, Copilot) and use them well. Faster output, but you understand and stand behind every line; you wouldn't approve sloppy AI-written code in review, so you don't ship it either.
• You're fine in a startup that changes direction. Decisions get made, then revisited.

Experience we expect with the stack

• Python: 6+ years
• FastAPI: 3+ years
• PostgreSQL / SQL
• Redis: 2+ years

Nice to have: RAG or vector search experience; LangChain or LlamaIndex; streaming over SSE, WebSocket or SignalR; Microsoft Graph and email integration work.

Benefits

• Be a driver of innovation in one of Oslo's most exciting AI ventures
• Work with talented peers in a collaborative, high-energy team
• Shape both product and culture as we grow
• Flexible, English-speaking environment