Founding Senior Product Engineer

Partnering with a well\-backed seed\-stage AI company in London, Foundation Partners are hiring for several founding Senior Engineers to a technically strong \& lean Eng team, shape 'how' in addition to 'what' is built and help the company prepare for the next iteration of their scaling journey.

The Role

This is a full\-stack product role with a backend\-heavy centre of gravity. You'll own complete product slices end\-to\-end and you'll ship these without needing to be guided.

You're not a specialist who hands off at the API boundary. You think in user outcomes and delivery units, and you're reliable: your code handles edge cases, your APIs have clean contracts, and the work you ship stays shipped.

What You'll Do

• Own product delivery — take features from spec to production, backend\-first but covering frontend and integration where needed


• Build and maintain backend systems — product APIs, data pipelines, and core infrastructure on our Python/FastAPI/Postgres stack


• Build with LLMs and agents — ship product features with significant LLM integration; contribute to the voice agent backend and information extraction systems


• Work across the stack — ship workable React/TypeScript frontend for product features; not a frontend specialist, but comfortable and pragmatic


• Collaborate with product and design — translate ambiguous requirements into concrete shipped work; be the engineer who unblocks, not the one who waits


• Maintain quality at speed — handle data integrity, error paths, API evolution, and operational concerns as a default, not an afterthought

• Independent delivery \- You can own and ship end\-to\-end product slices with minimal supervision; your track record shows features that shipped, stuck, and scaled


• Product trade\-off judgment — you balance speed, quality, and user impact under ambiguity; you push back when something is underspecified and make pragmatic calls when it needs to ship


• Reliability and API discipline — you handle data integrity, error paths, idempotence, and API versioning as standard practice; production reliability is your default, not a later concern


• Cross\-functional pragmatism — you work effectively with product and design, can unblock yourself across the stack, and ship workable frontend when that's what's needed

• Python backend (FastAPI or equivalent, async patterns, Postgres, Redis)


• LLM integration — building products where AI is in the critical path, not bolted on


• API design and data modelling


• JavaScript/TypeScript — comfortable enough to ship frontend features and review frontend PRs

• Experience with voice agents or real\-time audio pipelines


• Familiarity with evals, guardrails, or agent observability


• Familiarity with GCP / cloud infrastructure


• Experience in recruiting tech, marketplaces, or matching systems

A modern Python stack: FastAPI, Postgres, Redis, Docker, Pydantic AI, running on GCP. Frontend in React/TypeScript. We iterate fast and keep the codebase clean.

We'll offer you

• Above market salary


• Meaningful equity


• Full private healthcare \& dental


• Fertility benefits \& enhanced parental support


• Gym membership \& wellness benefits


• LOTS of Claude tokens


• Regular socials, offsites and an annual trip


• MacBook Pro \+ team kit


• "Whatever you need" approach to tools and support

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