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# Senior Fullstack Engineer (up to £140k)

- **Company:** Dex
- **Location:** Epsom, United Kingdom
- **Experience:** Expert
- **Salary:** £140,000
- **Contract:** Voluntary work
- **Skills:** Microsoft Word, Microsoft Excel, Application Programming Interfaces (APIs), Spreadsheets, Software Quality, Python (Programming Language), PostgreSQL, Microsoft PowerPoint, Software Architecture, TypeScript, AI Infrastructure, ReactJS, Large Language Models, Multi-Agent Systems, Fastapi
- **Published:** November 13, 2026
- **Apply:** https://www.apply4u.co.uk/jobs/senior-fullstack-engineer-up-to-140k/55867647

## About the Role

4+ years building and shipping production software at a venture-backed startup or top-tier tech company, with demonstrated ownership of features from ideation to production.

Strong fullstack fluency across Python (FastAPI), TypeScript, React, and PostgreSQL.

Experience building user-facing products tightly coupled to LLMs and autonomous agents, rather than just consuming basic completion endpoints.

An appetite for deep problem domains and a high bar for craft when building for demanding finance professionals.

## Description

Private equity deal teams manage billions of dollars using fragmented knowledge bases and manual workflows across Word, Excel, and PowerPoint. This team built a dedicated agentic AI platform that automates sourcing, diligence, and document authoring for multi-billion-dollar buyout and private credit funds. Backed by leading enterprise investors and scaling ARR more than 10x over the past year, they have achieved rare product-market fit in a notoriously hard-to-penetrate enterprise market.

You will join as a Senior Fullstack Engineer owning major product surfaces end-to-end, taking ideas from whiteboards to production and measuring real user impact. This is not about skinning third-party API wrappers with generic frontends. You will build user experiences tightly coupled to custom underlying infrastructure, including an in-house streaming agent harness, a resumable code execution framework, and multimodal document search engines.

The work

Own core product surfaces across the entire stack using Python, FastAPI, TypeScript, React, and Postgres, from architecture to post-launch telemetry.

Build complex user workflows directly on top of internal AI infrastructure, including streaming agent execution, end-to-end citations, and resumable code environments.

Design interfaces and authoring experiences that integrate deeply into the daily tools investment teams live in, such as spreadsheets, presentations, and email.

Uphold code quality, system performance, and architectural decisions that help a fast-moving engineering team sustain high shipping velocity.