Full Stack Engineer; TDD​/C# ​/JavaScript

Position: Full Stack Engineer (TDD / C# / JavaScript)
Location: South East London

Full Stack Engineer (TDD / C# / JavaScript) We are hiring a Full Stack Software Engineer with a strong test-driven development (TDD) background to help build the next generation of a mission-critical cybersecurity and communications platform used globally. This is a hands-on role focused on designing and delivering partner API integrations across a complex security ecosystem - including endpoint protection, network security, user awareness tooling, and monitoring systems.

You’ll work as part of a collaborative product team alongside full stack and front-end developers, supported by QA and Dev Ops, reporting into engineering leadership. Why This Role Matters The next-generation platform will provide customers with a unified view of security across distributed environments. As integrations expand, maintaining a high bar for quality, reliability, and test coverage is critical. This role will also play a key part in strengthening TDD practices across the team - leading through code and delivery.

What You’ll Do Design and build API integrations across a cybersecurity-focused product stack Deliver clean, maintainable full stack solutions using .NET and modern JavaScript frameworks Lead by example in test-driven development practices Integrate third-party systems using REST APIs, OAuth2, webhooks, and resilient patterns Contribute to a scalable, observable integration layer Collaborate with Product, QA, and Dev Ops to deliver high-quality releases Use AI-assisted development tools as part of your daily workflow Requirements (Must Have)

Experience with C# / .NET Core Strong experience with ASP.NET Core / Web API Modern JavaScript / Type Script experience

Experience with a component-based SPA framework (e.g. Vue, React, or Angular) Proven, hands-on test-driven development experience Strong experience integrating third-party APIs (REST, OAuth2, webhooks, retries, rate limiting) Solid SQL skills (e.g. Maria

DB or MySQL)

Experience with Git workflows (branching, pull requests, code reviews) Regular user of AI-assisted development tools (e.g. Claude Code, Cursor, Copilot or similar) Strong ownership mindset and commitment to quality Nice to Have Commercial experience integrating AI APIs (e.g. Claude, Bedrock, OpenAI or similar)

Experience with AWS (e.g. EC2, RDS, Lambda, S3) Microservices or distributed systems experience Familiarity with iterative product development methodologies Awareness of secure-by-design principles (e.g. ISO 27001) Background in SaaS or cybersecurity environments Benefits Hybrid working Excellent career development / Training budget Flexible working If you take pride in writing well-tested, production-grade code and want to contribute to building critical cybersecurity software used at global scale, we’d love to hear from you.

Full Stack Engineer (TDD / C# / JavaScript)