Principal Software Engineer (Full Stack) - React, Typescript, C#, .NET Core, MySQL, AWS Services (serverless)

Principal Full Stack Engineer – React, Typescript, C#, .NET Core, MySQL, AWS Services (serverless)

Outstanding permanent opportunity to join this global, market leading, B2B SaaS tech business as a Principal Engineer (Full Stack) / Lead Full Stack Developer with deep expertise in React, Typescript, C#, .Net Core, MySQL, AWS Serverless Services and event driven architecture. This business is embracing AI and bleeding edge development practices and offers the opportunity to help them to evolve and automate their Platform as a Service (PaaS) environment.

What You’ll Be Doing:

• Own architecture and technical decisions across squads; accountable for how software is built and shipped.
• Design and develop distributed, scalable microservices (C# .NET Core or Node.js) and REST/JSON APIs.
• Build modern React + TypeScript UIs with component-driven design, advanced state management, and reusable frameworks.
• Leverage AWS services (Lambda, API Gateway, SQS/SNS, Step Functions, S3, IAM) to deliver secure, event-driven systems.
• Embed testing-first practices (TDD/BDD, contract tests, Jest/RTL, Playwright/Cypress, xUnit/NUnit) to raise code quality.
• Implement modern CI/CD (GitHub Actions) and Infrastructure as Code (Terraform, CloudFormation, AWS CDK).
• Model secure-by-design principles; ensure robust authentication/authorisation (OAuth2, JWT) and data governance.
• Mentor engineers, set patterns, run PoCs, and unblock complex problems across squads.
• Champion “Always ship each cycle”; partner with Product to balance scope, delivery, and quality.
• Drive modernisation: sunset legacy code, reduce tech debt, and improve performance, reliability, and observability.

Who We’re Looking For:

• Highly experienced full stack engineer with strong proficiency in C# .NET Core and/or Node.js, plus React + TypeScript expertise.
• Proven experience designing event-driven, microservices architectures on AWS with secure, scalable patterns.
• Deep knowledge of API design, integration, and auth (OAuth2, JWT), with end-to-end performance focus.
• Strong database fundamentals with MySQL/Aurora: schema design, query optimisation, and performance engineering.
• Hands-on leader: comfortable coding ~40%+ of the time while guiding architecture across squads.
• Fluent with testing strategies across the stack and quality gates (coverage thresholds, PR checks, static analysis).
• Experienced with CI/CD and IaC (GitHub Actions, Terraform, CloudFormation, AWS CDK) and Git workflows.
• Security-minded with experience using tools like Sonat/Snyk/AppCheck for CVE remediation.
• Excellent collaborator and communicator with Product, QA, Security, DevOps, and Design stakeholders.
• Pragmatic, outcome-oriented, and energised by mentoring others and solving hard engineering problems.

£115k-£120K + bonus + benefits. London & 95% remote