Senior Frontend Engineer

Role: Senior Frontend Engineer (React / TypeScript) Location: London, hybrid (2–3 days per week in office) Salary: c£90k + 10% bonus + benefits Tech: React 18, TypeScript, TanStack Query, Vite, Tailwind, Radix/shadcn, Vitest, React Testing Library, MSW, Azure Immersum are partnering with a rapidly growing Fintech business operating in the FX and payments space who are looking for a Senior Frontend Engineer to join an autonomous engineering team. This is a role for someone who wants to build and own products, rather than simply adding features to an established platform. You will have ownership from the initial design and first commit through to production, with the freedom to make architectural decisions and be accountable for what you build. The Company: This global Fintech business is transforming how businesses and financial institutions move money internationally. Operating across FX, payments and banking infrastructure, they are building a high-volume platform where reliability, scalability and correctness are critical. The engineering environment is fast-paced and highly autonomous, with short paths between making a decision and getting it into production. Engineers are trusted to build, deploy and run the software they own. The Role: You will be responsible for designing and building new functionality within a modern React single-page application, working across areas including client onboarding, accounts and KYC/KYB. This isn't a role where you'll spend your time working on an established product and incrementally adding features. They're looking for a builder who enjoys taking ownership of a problem, designing the solution, building it and getting it into production. You'll be working on complex, form-heavy applications used by real customers, including multi-step onboarding journeys, branching validation, cross-field dependencies and workflows where clients may leave and return later. You'll need to be comfortable reasoning about where state should live, how it behaves across reloads and how the frontend orchestrates complex interactions with backend APIs. You'll also have genuine influence over how the frontend is built. You'll make architectural decisions within your domain, document and present those decisions to the wider tribe, challenge ideas when necessary and commit once a decision has been made. The team places a strong emphasis on quality rather than simply shipping code. Thorough testing, accessibility, security, reliability and observability are expected to be built into the software from the start. You'll also be expected to take ownership beyond your own code — reviewing pull requests, raising engineering standards and helping less experienced engineers develop. Technology: React 18 / TypeScript (strict mode)ViteTanStack Query / Form / RouterTailwind CSSRadix / shadcn component systemVitest / React Testing Library / MSWAzure Static Web AppsAzure DevOps / CI/CDGrafana & Application InsightsStorybookClaude Code / AI development tooling What they're looking for: Strong commercial experience building modern React and TypeScript single-page applications that are running in production with real usersExperience building complex, form-heavy applications with branching validation and cross-field dependenciesStrong understanding of multi-step application flows and frontend state managementDeep experience with TanStack Query, including query-key design, cache invalidation, stale policies and prefetchingExperience integrating with third-party services and APIs, ideally including identity verification, document upload or generated API clientsStrong understanding of roles and permissions, including enforcing them appropriately within the frontendA strong testing mindset, with experience using tools such as Vitest, React Testing Library and MSWExperience building accessible applications, ideally against WCAG 2.1 AAExperience with component systems such as Radix/shadcn and/or StorybookA genuine builder mentality — someone who enjoys taking ownership from idea/design through to productionComfortable making architectural decisions, explaining and defending them, and taking accountability for the resulting implementationStrong communication skills with both technical and non-technical stakeholders, including the confidence to disagree constructivelyExperience using AI development tools in practice, with the judgement to understand when they add value and when they don'tStrong engineering standards around security, reliability, observability and testing Useful, but not essential: Auth0 or a similar identity providerSentry or similar error tracking/observability toolsAzure Static Web Apps and Azure DevOpsVite build and bundle optimisation, including chunk splitting, bundle analysis and source mapsExperience within regulated financial services, KYC/KYB or client onboardingStorybook or another documented component libraryReal-time updates using WebSockets or SignalR Experience within payments, FX, banking, KYC/KYB, client onboarding or other financial systems would be useful, but isn't essential. If you're a Senior Frontend Engineer who wants genuine ownership, enjoys building products rather than simply maintaining them, and wants to work in an environment where architectural decisions and new software can move quickly into production, this could be a great opportunity to learn more.