Senior Full Stack Engineer

Hello! We're Solstice Analytics . Solstice Analytics is a payment and software service provider, headquartered in London serving small, local businesses across Europe. Founded in 2019, we build easy to use, integrated tools that enable our members to accept payments and boost business performance. At Solstice Analytics we believe small, local businesses are the lifeblood of our communities. We’re here because we don’t believe there’s a level playing field that gives small businesses with a fighting chance against the giants of the high street. We’re here because we see banks and legacy service providers making things harder for them. We don’t think the best technology or the best service should be reserved for those with the biggest headquarters. We’re here to fight for a future where small, local businesses can thrive, and to commit the same dedication they offer all of us. Become a part of our story. We’re looking for exceptional talent to join our mission. We offer a chance to create impact in a high-energy and connected culture, while benefiting from continuous learning opportunities, a supportive community which is proud to serve our mission, and comprehensive benefits. Role description We are seeking a highly skilled and passionate Senior Full Stack Engineer to join our ePOS Integration team, with a specialised focus on building and scaling the frontend experience for our product and enhancing its supporting backend services: In this pivotal role, you'll design, develop, and maintain the partner developer web portal that empowers our integration partners and third-party developers to manage accounts, spin up sandbox environments, complete integration certifications, access development support, and navigate our API documentation. As a full-stack engineer, you'll work across the frontend and contribute to the backend services that power the portal. Your work will directly shape how partners build on top of our platform, from their first sandbox call to production go-live. You'll be joining an exciting remake of the product, meaning you'll have a foundational role in defining the web experience for partner developers from near the ground up. You'll translate complex integration and certification workflows into intuitive, secure, and high-performance developer interfaces, while supporting the backend services behind them, collaborating closely alongside product managers, UX/UI designers, backend engineers, and platform teams. Your expertise will be instrumental in delivering a developer experience that makes integrating with us fast, clear, and reliable. Key Responsibilities Lead the design, development, and delivery of scalable, responsive full stack features for the Business Account portal using React, TypeScript, and GraphQL, with ownership spanning both frontend implementation and integration with backend services. Work closely with product and design teams to understand merchant needs and translate complex financial workflows—such as transfers, scheduled payments, account management, and Strong Customer Authentication ( SCA ) flows—into secure, end-to-end user experiences backed by reliable APIs. Build and maintain data-rich, high-performance interfaces for transaction feeds, balances, statements, and multi-currency views, ensuring efficient data fetching, state management, and seamless interaction with backend services. Develop and maintain GraphQL schemas, resolvers, and API integrations, ensuring consistency between frontend requirements and backend data models while promoting type safety and end-to-end reliability. Write clean, maintainable, and well-tested code across the stack, applying strong TypeScript practices and contributing to overall system stability, security , and scalability. Actively participate in code reviews across frontend and backend contributions, helping establish engineering best practices in a team transitioning from a mobile-first to a full stack, web-capable organization. Identify and resolve performance bottlenecks, data inefficiencies, and production issues across the full stack, ensuring a smooth, reliable experience for merchant users. Stay up-to-date with the latest frontend technologies, trends, and best practices, applying them to enhance our merchant-facing web platform. Your Story 5+ years of professional experience in frontend/web development. Expert-level proficiency in TypeScript , including advanced type manipulation, generics, and understanding of complex type inference. Strong proficiency in React.js and its core principles, developed with a type-safe approach. Experience supporting Backend services in Java and Spring Boot Extensive experience with Next.js for server-side rendering, static site generation, and API routes, with a focus on TypeScript integration. Solid understanding of modern JavaScript (ES6+), HTML5, and CSS3. Experience with state management libraries (e.g., Redux, Context API, Zustand) in a TypeScript environment. Strong experience consuming GraphQL APIs (e.g., Apollo Client), wit