Senior Fullstack Engineer at Series A financial AI startup

Jack & Jill; Greater London; On-site; GBP 90,000 - 140,000; Full time

Job summary

Jack & Jill, a London-based Series A financial AI startup, seeks a Senior Fullstack Engineer to own and ship end-to-end features. You’ll work with Python, FastAPI, and React to build data processing and AI tooling within a lean team.

Ideal candidates have 4+ years building production software at high-growth tech firms, deep Python and TypeScript/React expertise, and a strong distributed systems background. You’ll impact high-value financial workflows.

Qualifications

• 4+ years of experience building production software at a venture-backed startup or high-performance tech firm.
• Deep expertise in Python and TypeScript/React, with a strong background in distributed systems and LLM implementation.
• A product-focused mindset that prioritizes user impact and excels at delivering high-quality code in a fast-paced environment.

Responsibilities

• Architect and ship end-to-end features using a stack of Python, FastAPI, and React to solve complex data challenges.
• Develop robust, interruptible execution frameworks for AI agents and maintain sophisticated search clusters.
• Create collaborative AI tooling that integrates with standard enterprise productivity suites to streamline professional workflows.

Skills

Python

TypeScript/React

Distributed systems

LLM implementation

Product mindset

Tools

FastAPI

React

Job description

Job Title

Senior Fullstack Engineer

Salary

Not Disclosed

Company Description

Series A financial AI startup

Job Description

You will lead the development of an agentic platform designed to automate complex workflows within the financial services sector. By owning product surfaces end-to-end—from architecture to deployment—you'll build sophisticated tools for data processing and AI-driven collaboration, directly impacting high-value investment operations while working alongside a lean, elite engineering team.

Location

London, UK

Why this role is remarkable

• Full ownership of entire product surfaces within a high-growth engineering culture that minimizes bureaucracy.
• Backed by top-tier VCs following a period of massive revenue growth and a successful Series A funding round.
• Build complex, streaming-first agentic frameworks and AI systems that solve real-world problems in a multi-trillion dollar industry.

What You Will Do

• Architect and ship end-to-end features using a stack of Python, FastAPI, and React to solve complex data challenges.
• Develop robust, interruptible execution frameworks for AI agents and maintain sophisticated search clusters.
• Create collaborative AI tooling that integrates with standard enterprise productivity suites to streamline professional workflows.

The ideal candidate

• 4+ years of experience building production software at a venture-backed startup or high-performance tech firm.
• Deep expertise in Python and TypeScript/React, with a strong background in distributed systems and LLM implementation.
• A product-focused mindset that prioritizes user impact and excels at delivering high-quality code in a fast-paced environment.