Full Stack Engineer

FlexTrade; City Of London; On-site; GBP 70,000 - 105,000; Full time

Job summary

FlexTrade UK Ltd. is seeking an experienced full-stack developer to join the FlexONE team. You will work on Scala/Play backend and React/AG-Grid frontend, contributing from an MVP to a full-featured web and mobile companion app.

Based in London with our UI-focused team, you will own design, migrations to React Native, testing, and collaboration with desktop teams to ensure feature parity. Strong communication and ownership are essential to thrive in our fintech environment.

Qualifications

• Deep full stack expertise and production web app experience.
• Significant experience in React and modern TypeScript.
• Willingness to own backend (Java/Scala preferred).
• Experience building or maintaining cross‑platform mobile apps.

Responsibilities

• Design & Build: deliver robust features across Scala/Play backend and React/AG‑Grid frontend.
• Mobile Migration: plan migration from CodenameOne to a JS framework (likely React Native).
• Quality & Reliability: champion testing, observability, and performance.
• Team Growth: mentor engineers, assist with hiring and onboarding as the team scales.
• Collaboration: ensure feature parity with the Desktop app team.
• Backend: Scala, Play Framework, REST/JSON and gRPC.
• Frontend: React, TypeScript, AG-Grid.
• Mobile: migrate to React Native or similar JS cross‑platform framework.

Skills

Deep full stack expertise

React

TypeScript

Java/Scala experience

Mobile capability

Communication

Tools

Scala

Play Framework

REST/JSON

gRPC

CodenameOne

React Native

Job description

FlexTrade Systems is a provider of customized multi-asset execution and order management trading solutions for buy- and sell-side financial institutions. Through deep client partnerships with some of the world's largest, most complex and demanding capital markets firms, we develop the flexible tools, technology and innovation that deliver our clients a competitive edge. Our globally distributed engineering teams focus on adaptable technology and open architecture to develop highly sophisticated trading solutions that can automate and scale with your business strategies.

At FlexTrade, we hold our values close to heart, with pride and gratitude, as they guide us in everything that we do. We are dedicated to giving our clients a competitive edge, taking ownership of our responsibilities, being flexible to adapt to ever changing environment and technology, bringing integrity to ever interaction and we continue to improve, grow together and collaborate as one team. All of these while having fun truly makes FlexTrade a wonderful place to work.

The Team

We are looking for an amazing developer to join our team building FlexTrade's OEMS platform, FlexONE, which is our state-of-the-art, fully integrated Order Management System and Execution Management System. This system was built from the ground up starting in 2013 and is written entirely in Scala.

The FlexONE team is split between our Milwaukee office, where the product was first developed, and our London office, which is now predominantly responsible for development of the UI for the application.

The London team is an experienced group of Java and Scala developers, with a deep understanding of UI and UX design. We deliver our software using agile methodologies, and we encourage best practices such as TDD, code reviews and pair programming for knowledge sharing and learning. Our team owns all aspects of the features they work on, from designing solutions to meet customer or product requirements, through implementation, QA and delivery. Each team member works on every part of the system.

About You

Be part of our FlexONE team and own critical product surfaces across our web and mobile applications. You'll work end-to-end across a Scala + Play Framework backend, and a React + AG-Grid front-end, using gRPC for communication with our core product's backend systems. You will lead the technical direction as we build our Web app from an MVP to a comprehensive companion to the desktop application, as well as continuing the evolution of our Mobile app.

Responsibilities

• Design & Build: Deliver robust, maintainable features across the stack (Scala/Play backend, React/AG-Grid frontend)
• Mobile Migration: Define the path from Codename One to a JS-compatible framework (likely React Native), including architecture, incremental migration strategy, and performance/UX parity
• Quality & Reliability: Champion code quality, testing, observability (metrics, logs, tracing), and performance across the stack
• Team Growth: Mentor engineers, assist with hiring, onboarding, and capability development as the team scales.
• Collaboration: Partner closely with the Desktop application development team to ensure feature compatibility and parity
• Backend: Scala, Play Framework, REST/JSON and gRPC
• Frontend: React, TypeScript, AG-Grid
• Mobile: Current app in CodenameOne, target migration to React Native (or similar JS-based cross-platform framework)

Requirements

• Deep full stack expertise
• Experience building & deploying production web apps, with significant experience in React and modern TypeScript
• Willingness to take ownership of backend (Java/Scala experience preferred but not required)
• Mobile Capability: Experience building or maintaining cross-platform Mobile Apps
• Architecture & Design: Solid grasp of API design, web & mobile architecture, as well as good UX design.
• Communication: Clear, pragmatic communicator who collaborates well with both engineers and non-engineers.

FlexTrade Systems, Inc. is an equal opportunity employer and makes employment decisions without regard to race, color, religion, sex, sexual orientation, gender identity, national origin, protected veteran status, disability status, or any other status protected by law.

FlexTrade UK Ltd. conducts a pre-employment screening which consists of a Criminal History, Background and Credit Check for successful candidates.