Senior BE AI Engineer (Python) - AI Agent Systems

We’re Sloneek, a European HR tech startup on a mission to change HR for the better. ~40 people across Europe, fresh $6M round closed 💰, and an AI layer - Sloneek Intelligence - that is the differentiator of our product: LLM agents that automate HR work and answer real questions over real company data.

Sloneek Intelligence is past the prototype stage. It runs in production, real customers use it daily, and we've learned exactly where agentic systems break at scale. Now we're hiring a very senior backend engineer to shape its architecture. You'll join a tight six-person team — backend, frontend, QA, data engineer, PM, and our CTO — working directly with all of them and owning backend decisions end to end.

🛠️ The actual work

• Design and build the Python/FastAPI services and APIs that power Sloneek Intelligence — connecting agents, the core HR platform, data services, and the frontend

• Multi-agent orchestration: domain agents, inter-agent contracts, data handoff between agents without corruption

• Data layer for LLM systems: how agents query and work with real company data at scale — without dragging it all through model context

• Evaluation infrastructure: test sets that reflect production, model benchmarking, LLM judges

• Production reliability: latency, token budgets, timeouts, auth, observability — the boring things that make AI products trustworthy

⚙️ Stack: Python · FastAPI · MCP · PostgreSQL · OpenAI APIs (Responses API, reasoning models) · Kubernetes · AWS

✅ You're a fit if you

• Have deep backend experience and have designed backend systems yourself — architecture is your decision, not your ticket

• Have shipped LLM-powered features to production — agents, RAG, or serious API orchestration. This one is a must. You know what breaks: context limits, hallucinated synthesis, eval blind spots

• Have kept real systems alive under real load, more than once, and own the story — what you decided, what broke, what you'd redo

• Write tests and believe in them

• Use AI in your daily engineering work — concretely, currently, and can show it

• Think user-first when pushed, not just architecture-first

❌ You're not a fit if your AI experience is demos and prompt glue, or if you're an ML researcher looking for a research role. This is hard backend engineering where the hardest component happens to be an LLM.

💜 Why join

• Shape the architecture of the AI product a growing European company is betting on — with real production traffic and real consequences

• Small senior team, no corporate layers — decisions are owned, not passed around

• Remote-first 🌍 with real in-person time every 2–3 months; we hire for years, not gigs

• Fast and honest process: 3 conversations + a small take-home, typically 2 weeks to offer ⚡

If you’re passionate about backend architecture, AI integration, and building from zero with real impact, we’d love to hear from you.

Let’s reinvent HR together — one smart API at a time.