If you are a Full Stack JavaScript Developer with a proven track record of developing single-page applications, we have a new role we would like to discuss with you. Please note this role requires onsite attendance four days a week in Upminster, Essex.
The client is building a platform that guides consumers through the complete online customer journey, from their first visit through identity verification, e-signature and submission.
As a Mid-Level Full-Stack JavaScript Developer, you'll work across the platform: a React single-page application on the front end, Node.js APIs and background workers on the back end, and Microsoft SQL Server as the system of record.
This is a hands-on product engineering role where you'll ship customer-facing journey steps, build and consume REST APIs, write database migrations and integrate third-party services behind clean, maintainable interfaces.
What you'll do
- Build and maintain customer-journey screens and shared components in React 19, using React Router 7, Vite and Sass/SCSS across multiple branded sites from a single codebase.
- Develop back-end features in Node.js, including a Fastify API, an Express backend-for-frontend and durable background jobs processed through a SQL-backed outbox queue.
- Design and evolve the SQL Server schema through forward-only migrations, using parameterised queries and transactional business logic.
- Integrate and mock third-party services, including identity-verification and lead-management providers, while keeping transport details behind well-defined interfaces.
- Write meaningful tests at every layer: Vitest unit and route tests, Testing Library component tests, and Playwright end-to-end journeys against a real database running in Docker.
- Build with the needs of a regulated consumer product in mind, including robust input validation, careful PII handling, audit trails, idempotent retries and graceful degradation.
- Work collaboratively to document technical decisions, follow established conventions and improve the platform as it grows.
What you'll bring
- At least three years of professional JavaScript development experience, with meaningful hands-on work across both front-end and back-end development.
- Strong React fundamentals, including hooks, controlled forms, routing and state management, together with confidence using modern ESM tooling.
- Experience building and consuming REST APIs in Node.js using Fastify, Express or a comparable framework.
- Practical SQL knowledge covering schema design, joins, transactions and indexes. SQL Server experience is helpful but not essential.
- A genuine testing habit: you write useful tests because they prevent defects and support confident delivery, not simply because the CI pipeline requires them.
- Clear written communication and the ability to document decisions, explain trade-offs and work within established conventions.
Nice to have
- Experience working on multi-tenant or multi-brand products.
- Familiarity with queue or outbox patterns, Redis, PM2, nginx or Cloudflare.
- Exposure to regulated industries such as financial services or insurance, or experience with KYC and identity-verification journeys.