Backend Engineer (AI Platform) - London

Backend Engineer (AI Platform) - London

£80k–£100k + EMI equity

About the Role

We’re hiring a Backend Engineer to build the core infrastructure behind Revax’s AI-native platform for professional services.

You’ll design, optimise, and scale the systems that power multi-agent drafting, knowledge graphs, and auditable AI workflows used by accountants, tax advisors, and consultants at leading firms. This is not a “ticket-taking” role -you’ll work directly with the founders, own critical backend services end-to-end, and help define how AI systems are built responsibly in regulated domains.

If you enjoy designing clean APIs, scaling Python services, and building systems that actually ship to paying c ustomers, this role is for you.

Compensation: £80,000–£100,000 base + EMI equity

Location: London

About Revax

Revax is building a new class of AI-native software for tax advisory firms.

Today, professional services teams spend countless hours drafting, reviewing, and re-drafting work - constrained by fragmented knowledge, manual workflows, and brittle tooling. We turn a firm’s own expertise into structured, auditable, AI-powered systems that draft, analyse, and explain deliverables with full provenance.

We’re a fast-moving, well-funded startup backed by leading angels, already working with major firms, and building at the intersection of AI agents, knowledge graphs, and real-world enterprise workflows.

What You’ll Do Build & own core backend systems

· Build and optimise databases for complex, real-world data

· Design and implement APIs using FastAPI for AI workflows and product features

· Build and scale LangGraph-based multi-agent systems with checkpointing, retries, and observability

· Integrate and scale vector search, knowledge graphs (Neo4j), and associated retrieval pipelines into production services

· Deploy and operate GPU-backed services for AI workloads (e.g. inference, embeddings, or agent pipelines) in production

Scale & operate production infrastructure

· Deploy services on GCP (Cloud Run / GKE) or equivalent cloud infrastructure

· Improve performance, reliability, and cost efficiency (latency, throughput, retries, backoffs)

· Implement security-first patterns: auth flows, service-to-service auth, IAM, and access controls

· Help prepare the platform for enterprise customers (SSO, auditability, compliance ready patterns)

Collaborate closely with founders & product

· Shape system architecture and API design alongside full-stack and ML engineers

· Translate ambiguous product ideas into robust backend implementations

· Iterate quickly based on real customer usage and feedback

What We’re Looking For

Essential

· 2-3 years building backend systems for real users

· Production experience with FastAPI (or similar modern Python frameworks)

· Solid understanding of API design, PostgreSQL, and distributed systems fundamentals

· Experience deploying and operating services on cloud infrastructure (GCP, AWS, and Azure)

· High ownership mindset: you care deeply about reliability, correctness, and outcomes

Strong Plus

· Experience with LangGraph, RAG pipelines, vector databases, or knowledge graphs

· Familiarity with Neo4j or graph-based data modelling

· Experience working on AI-native or agentic systems

· Comfort working in early-stage startups with ambiguity and speed

· Experience deploying and working with GPU services for AI workloads

Bonus

· Exposure to professional services, finance, tax, or regulated workflows

· You actively use modern AI coding tools (Cursor, Claude Code, etc.)

· Strong instincts for developer experience and internal tooling

Why Revax

· Real ownership over core backend infrastructure

· Work directly with founders on high-impact technical decisions

· AI-native product with real customers and immediate feedback

· Modern stack: Python, FastAPI, LangGraph, Postgres, Supabase, Neo4j, GCP

· Meaningful early-stage equity: we hire owners, not passengers

· A lean, low-ego, high drive team that ships fast and cares about their work

Practical details

· London based (strong preference for in office collaboration)

· Visa sponsorship available