Senior Software Engineer, JavaScript/TypeScript

React work that powers markets rather than another customer-facing product. You'll build the web and desktop applications traders and market operators use to run, monitor and control exchange infrastructure, technology this firm licenses out to other markets too. Ownership over ticket-shuffling, on a platform where unreliable code has a visible consequence.

The work

Most React jobs are another customer-facing product. This one powers technology used by financial markets around the world.You'll build the webapps and desktop tools that traders and market operators use to trade on, monitor and control exchange infrastructure. That technology doesn't just run here, it's licensed out and run by other markets too, so every screen you ship carries weight.You'll get ownership rather than a tightly defined list of tickets. Working with product, infrastructure, QA and UX, you'll shape the technical approach, challenge weak ideas and turn wireframes into reliable applications.You'll also influence how the team builds software: reviewing designs, raising engineering standards and supporting less experienced developers, without becoming a full-time manager. You don't need trading experience, but you should enjoy hard technical problems where poor performance or unreliable code shows.

What you'll build

You'll design and develop scalable applications and APIs in JavaScript, TypeScript and React, and integrate them with the Python APIs behind the platform. Your work will include:

• Building responsive, data-intensive web and desktop applications
• Integrating front-end applications with Python-based APIs
• Improving performance, accessibility, security and automated test coverage
• Contributing to technical reviews, CI/CD improvements and decisions on new tools and architecture

What you'll need

You don't need to be a Python engineer, but you'll work closely with Python APIs, so some familiarity helps. You should be comfortable with HTML5, CSS3, responsive design, browser compatibility and a Linux or WSL environment. Cloud platforms, Infrastructure as Code, containers or financial markets technology are useful, but none is essential.

• At least five years in front-end development, with strong commercial JavaScript, TypeScript and React
• Experience building data-driven applications where performance, reliability and usability matter
• A solid grasp of automated testing across unit, integration and end-to-end

How the team works

You'll report to a Lead Software Engineer and join a team that values practical ideas, shared ownership and direct communication. People are trusted to make decisions, but you won't be left to struggle alone: work is reviewed openly, knowledge is shared, and senior engineers are expected to raise standards rather than protect their own corner. The London team is in the office at least three days a week, with the rest available for home working.The full interview process is shared in the first confidential conversation.