Robert Half Technology are assisting a market leading financial services organisation to recruit a React Developer on a contract basis. Hybrid working - London based Role The React developer will be working on the build of a product-grade React & Typescript application from greenfield through to a maintainable, globally scalable, and secure product Greenfield build to production: build a production-grade React & TypeScript application from zero to a maintainable, scalable platform Data-dense UI delivery: Deliver high-quality UI for dashboards, tables/grids, filtering/sorting, drilldowns, forms, and multi-step workflows State & data patterns: implement robust client-state and server-state patterns including loading/error states, retries, resilience, caching and invalidation Performance engineering: Drive render efficiency, bundle size control, code splitting, virtualisation for large datasets, network efficiency, and instrumentation/observability API contract collaboration: Work with backend engineers on predictable API contracts via BFF (pagination, aggregation shapes, response models, error semantics) Security-by-design delivery: Apply secure front-end practices (auth/session hygiene, safe client-side data handling, dependency hygiene) Accessibility & usability: Ensure keyboard support, focus management, ARIA where appropriate, and strong empty/error states for complex UIs Quality discipline: Maintain a strong quality bar through code review, automated tests, CI quality gates, and release readiness Delivery pipelines: Contribute practically to build tooling, CI checks, deployment considerations and environment configuration Documentation: Produce concise, proper documentation for key decisions, patterns and non obvious implementation details Profile The React Developer will have significant commercial experience within financial services, building modern React applications (hooks, composition patterns, controlled/uncontrolled components, state lifting, modularisation Demonstrated ability to operate as a senior engineer: strong judgement, proactive risk management, pragmatic delivery, and high code quality standards Proven ability to design front-end architecture for long-term maintainability (module structure, feature boundaries, shared UI patterns, conventions) Comfortable establishing foundations early (linting/formatting, project structure, testing strategy, patterns for API access, error handling, and observability hook) Experience shipping complex interface: tables/grids, dashboards, rich filters, multi-step workflows, and interaction-heavy UIs Familiarity with performance constraints caused by large datasets and frequent UI interactions (virtualisation, event handling) Strong TypeScript capability across: typed component APIs (props/contracts), shared domain models/DTOs, safe typing around API responses, error and async flows, sensible user use of generics/utility types without over-engineering Proven judgement selecting and implementing state patterns: clear separation of UI state vs server state, caching & invalidating strategies, avoiding unnecessary re-render and state leaks Experience with modern tooling such as TanStack Query Strong awareness of security/performance best practices in client data fetching and caching (handling auth/session, sensitive data considerations, preventing accidental data leakage, safe error handling) Experience writing and maintaining meaningful automated tests with a strong judgement on what to test, keeping suites fast and avoiding brittleness Evidence of improving real-world performance (bundle analysis, render optimisation, code splitting, virtualisation) Ability to keep UI responsive under heavy interaction patterns and large datasets. Security-conscious delivery Security-minded development practices (OWASP awareness, auth/session hygiene, dependency hygiene) Comfortable operating in environments where confidentiality, disciplined change control and auditability matter Data visualisation (interactive charts; performance-conscious rendering) Company Market leading financial services organisation with offices in London Hybrid working - London based Salary & Benefits The salary range/rates of pay is dependent upon your experience, qualifications or training. Robert Half Ltd acts as an employment business for temporary positions and an employment agency for permanent positions. Robert Half is committed to diversity, equity and inclusion. Suitable candidates with equivalent qualifications and more or less experience can apply. Rates of pay and salary ranges are dependent upon your experience, qualifications and training. If you wish to apply, please read our Privacy Notice describing how we may process, disclose and store your personal data: roberthalf.com/gb/en/privacy-notice.