Full Stack Engineer

Primis; Greater London; Hybrid; GBP 80,000 - 100,000; Full time

Benefits offered by this job

ChatGPT Pro subscription

London office

Direct line to CTO

Job summary

Primis is hiring a Full Stack Engineer to join a fintech startup in London with hybrid flexibility. You’ll own features end-to-end, working directly with the CTO in a small, technically focused team.

The product provides portfolio intelligence for treasuries and financial institutions, with live paying clients and equity options. You’ll build React/TypeScript interfaces, develop FastAPI services, and explore AI-enabled workflows to improve portfolio analysis and scenario modelling.

Qualifications

• 3+ years building web apps commercially with React, TypeScript and Python backend.
• Experience with async workflows and data consistency.
• AI-native work: leverage AI tools while validating output and code.
• Owned shipped features and explained trade-offs.
• Breadth over specialization with full-stack startup/scale-up exposure.
• Interest in finance; fintech/crypto experience is a plus.

Responsibilities

• Build React and TypeScript interfaces for portfolio analysis and decision support with strong UX.
• Develop Python (FastAPI) services, APIs and data integrations.
• Take features from idea to production and own the result.
• Integrate AI into the product in meaningful, user-focused ways.

Skills

React

TypeScript

Python backend

Tools

FastAPI

Job description

Full Stack Engineer – Portfolio Intelligence Fintech

London (hybrid flexibility) | £80,000–£100,000 + equity | Permanent

My client is a funded, early-stage fintech building portfolio intelligence software for corporate treasuries, stablecoin issuers and financial institutions. Their platform brings portfolio analysis, risk management, scenario modelling and investment comparison into one product, helping teams decide where their cash and digital assets should sit.

The founding team comes from leading hedge funds, global banks and blockchain infrastructure. The product is live, with paying clients across banking, stablecoins and corporate treasury, and they’ve just secured further funding to grow the engineering team.

They’re hiring a Full Stack Engineer to work directly with the CTO, owning features end to end and helping shape the product at an early stage.

What you’ll do

• Build React and TypeScript interfaces for portfolio analysis, scenario modelling and investment decisions, with real care for the user experience
• Develop the Python (FastAPI) services, APIs and data integrations behind them
• Take features from idea to production: make the architecture calls, ship, and own the result
• Build AI into the product in ways that are actually useful, from exploring a portfolio to comparing scenarios

What they’re looking for

• 3+ years building web applications commercially, with strong React and TypeScript and practical Python backend experience
• Experience below the framework: async workflows, data consistency, partial failures, and what to do when connected services disagree
• AI-native: you get real leverage from agents and AI tools, but you still check the output and understand the code
• A track record of owning shipped features and explaining the trade‑offs you made
• Breadth over specialism: you’ve worked across the stack, ideally in a startup or scale‑up
• Curiosity about finance. Fintech payments investing or crypto experience is a plus, but not essential

What’s on offer

• Company‑paid ChatGPT Pro or Claude Pro subscription
• Modern office in central London
• Real ownership and a direct line to the CTO in a small, technical team