Senior Backend Engineer

Senior Backend Engineer | AI 0→1 Product | London (Onsite) 💰 Competitive Salary + Equity | Pre-Series A This isn't another backend role maintaining a mature platform or picking up tickets from a backlog. We're partnering with a well-funded AI startup building a completely new product from 0→1 — and looking for an engineer who gets excited by a blank page. You'll work directly with the CTO and founders, making real architectural decisions and taking ideas from "could we build this?" all the way to production and real users. What you'll be doing: Architect and build the backend from the ground up - genuine input into system designTake ideas from 0→1 through architecture, implementation, deployment and iterationBuild high-performance APIs, background workers, data pipelines and third-party integrationsDesign and ship AI agent workflows, including LLM orchestration, tool calling and retrievalSolve problems around latency, reliability, observability, cost and model performanceWork directly with the CTO and founders - no layers between you and the decision-makersShip to real users, learn from what breaks, and improve it What we're looking for: Excellent software engineering and CS fundamentalsStrong production experience with PythonStrong backend/API engineering experienceExperience building and shipping 0→1 products or significant greenfield systemsSolid understanding of distributed systems, databases, concurrency and asynchronous processingHands-on experience with LLMs, AI agents, RAG, embeddings or model-driven applicationsSomeone who can take an ambiguous problem and work out the architecture rather than waiting to be toldA track record of shipping - GitHub, products, side projects, startups, whatever proves you build You'll stand out if you've worked with: FastAPI / Django · PostgreSQL · AWS · Redis / Celery / Kafka · Vector databases · Agent orchestration / tool calling · RAG / retrieval systems · LLM evaluation and observability · AI-native products · High-growth startups · Strong open-source projects Top university CS backgrounds are valued, but what you've actually built matters more than where you studied. Why this is different: you won't be joining a large engineering org owning a small slice of a service nobody understands. You'll be one of the engineers actually building the thing — direct access to decision-makers, meaningful equity, and real technical ownership before the architecture is set in stone. Highly customer-facing, solutions-driven engineers - must have come from a startup environment. Industry background is not a limiting factor. 📩 Get in touch to hear more.