_Haystack is working with an employer on this opportunity!_ Backend Engineer – Fintech Scale-Up 💰 £70,000–£90,000 📍 London (Options for full remote working or hybrid working in the London office) 🕓 Full-time | Permanent About the Company We’re partnered with a high-growth fintech scale-up building modern financial infrastructure that’s changing how people and businesses move money globally. Their platform powers real-time payments, automated compliance, and intelligent financial workflows used by leading UK and international clients. They’re now looking for a Backend Engineer to help design, build, and scale systems that sit at the heart of their platform — from secure transaction processing to high-availability APIs serving thousands of requests per second. You’ll join a small, talented engineering team working in a fast-moving environment where new ideas are encouraged, ownership is expected, and your impact will be visible from day one. The Role You’ll play a key role in designing and maintaining backend systems that keep mission-critical financial data flowing smoothly and securely. The ideal candidate loves solving complex problems, writing clean, testable code, and collaborating across teams to ship production-ready features. What You’ll Do - Design, build, and maintain distributed backend systems and APIs for payment processing, data exchange, and reporting. - Collaborate with product, data, and DevOps teams to deliver new features end-to-end. - Ensure performance, reliability, and scalability across core platform services. - Implement best practices around testing, observability, and security in production. - Participate in code reviews, technical discussions, and architecture decisions. - Contribute to the continual evolution of the company’s engineering standards and culture. Tech Stack - Languages: Node.js (TypeScript) - Frameworks: FastAPI, Express, or similar - Databases: MongoDB - Cloud: AWS (Lambda, ECS, S3, RDS), Docker - Tooling: GitHub, Terraform, CI/CD pipelines - Bonus: Experience with financial APIs, Kafka, or event-driven systems About You - 3+ years of backend development experience in production environments. - Strong understanding of API design, data modelling, and microservice architecture. - Experience building systems that handle sensitive data or high transaction volumes. - Familiarity with cloud-native development and CI/CD pipelines. - Comfortable in a fast-paced environment, balancing technical depth with delivery. - Passionate about clean code, security, and reliability. Why Join - Work on cutting-edge fintech systems that power real-world transactions. - Join a collaborative, ambitious team where your voice genuinely counts. - Hybrid working model with flexibility around your schedule. - Competitive salary and benefits, with opportunities for progression. - A modern engineering culture focused on autonomy, quality, and impact. 💡 This is an opportunity to help shape the backend systems of one of the UK’s most exciting fintech scale-ups — where technical ownership meets tangible product impact.