Senior Software Development Engineer in Test (SDET)

About Lumen Dynamics Lumen Dynamics is an award-winning FinTech founded in Edinburgh, powered by a high-performing, remote-first team across the UK and beyond. Our platform gives e-commerce and technology businesses the freedom and flexibility to redefine how they handle payments. Since 2018, we’ve been pioneers in payment orchestration, enabling enterprise brands to optimise their infrastructure and create frictionless digital experiences. From travel giants to household retail names, our global customer base is growing fast, supported by world-class partners like Visa and Worldpay. The journey so far has been incredible, but we’re just getting started. We are looking for exceptional talent to join us as we level up our engineering maturity. About this role At Lumen Dynamics , we champion an inclusive, engineering-led approach to quality. Our Senior Software Development Engineer in Test (SDET) role is a position dedicated to architecting, building, and scaling our automated testing infrastructure and quality tooling. You will enable our teams to ship high quality software frequently and with total confidence by providing them with powerful, scalable testing tools and robust frameworks. This is not a traditional QA or "sign off" testing role. You will not sit at the end of a delivery pipeline manually validating tickets or acting as a gatekeeper. Instead, you are a core engineer. You will own the technical design, development, and evolution of our centralised automation frameworks and infrastructure. Your primary impact will be delivered through engineering systemic solutions that allow development teams to own their own quality and deploy safely. Whatyou’llbe doing Framework Architecture and Engineering: Design and build automation frameworks, covering Integration, Contract, E2E, and Performance / Load testing. Be informed and opinionated on what good looks like for Unit and Component tests. Tooling and Infrastructure Development: Build, maintain, and scale internal testing tools, libraries, and test data management utilities that streamline the development lifecycle for all engineering teams. CI / CD Optimisation: Engineer and manage fast, reliable, CI native pipelines. Implement advanced, parallelised quality gates and automated feedback loops directly into the deployment infrastructure to eliminate manual intervention. Architectural Testability: Analyse system architecture and cloud native topologies to suggest and implement improvements that enhance system testability and quality. Production Quality: Build out monitoring, logging, and alerting tooling and standards. Translate incident postmortem findings into concrete, automated safeguards and process improvements. Metrics and Diagnostics: Implement and track quality metrics to diagnose system bottlenecks, using data to drive targeted performance and reliability enhancements across our frameworks. Mentoring and Engineering Maturity: Proactively drive forward the organisation wide quality strategy, building and designing our testing ecosystem, and mentoring software engineers. Act as a thought leader to coach development teams, championing 'quality first' design to improve delivery speed and move the needle on engineering maturity. Whatwe’relooking for This role is for an engineer who is passionate about infrastructure, code quality, and framework design. We are looking for a technical specialist who thrives on solving complex automation challenges and building scalable software systems rather than writing and executing test scripts. Essential Experience Advanced Software Engineering Fundamentals: Deep proficiency in Java, TypeScript, or similar modern languages, with extensive recent experience operating as a core technical SDET. Framework Design from Scratch: A proven track record of designing, building, and scaling multi layered automation frameworks from the ground up (Integration, Contract, E2E, and Performance). CI / CD and Pipeline Engineering: Heavy hands-on experience building, optimising, and maintaining CI / CD pipelines, with a focus on fast, parallelised execution and automated gates. Cloud Native Architecture: Deep understanding of distributed system design, microservices, and cloud native environments, with the ability to optimise them for logging, observability, and testability. Root Cause Debugging: Exceptional technical debugging skills across complex, distributed systems, with the ability to write robust automated regressions to address production vulnerabilities. Technical Collaboration: Ability to define technical standards, document framework architectures clearly, and collaborate with engineering teams to ensure seamless adoption of quality tooling. Nice to Have Background experience as a Software Engineer. Experience implementing, capturing, and visualising DORA metrics automatically within deployment pipelines. Familiarity with feature flagging frameworks and progressive delivery infrastructure. Experience in fintech, payments, or other high throughput