Senior Software Engineer in Test in London

Nscale is the GPU cloud engineered for AI. We provide cost-effective, high-performance infrastructure for AI start-ups and large enterprise customers. Nscale enables AI-focused companies to achieve superior results by reducing the complexity of AI development. Our GPU cloud bolsters technical capabilities and directly supports strategic business outcomes, including cost management, rapid innovation, and environmental responsibility.

At Nscale, our SDETs play a critical role in building new testing frameworks for cutting edge AI and cloud technologies. We thrive on a culture of relentless innovation, ownership, and accountability, where every team member takes pride in their work and drives it with excellence and urgency. As an Nscaler, you’ll build trust through openness and transparency, where everyone is inspired to do their best work. If you join our team, you’ll be contributing to building the technology that powers the future.

About The Role (Job Purpose)

Nscale is seeking a Senior Software Development Engineer in Test (SDET) to help scale quality across our GenAI cloud platform through engineering, automation, and enablement, not manual testing or release gatekeeping, joining our existing compact team of engineers. You will act as a true quality multiplier across product squads – designing and maintaining test frameworks, CI quality pipelines, and internal tooling that allows teams to ship safe, observable and reliable features at high velocity. Developers own the quality of the features they build, and you will enable that ownership to scale.

What You’ll Be Doing (Responsibilities)

• Enable product teams to ship high-quality software by building testing systems, frameworks, and guardrails.
• Define and evolve quality standards and best practices and quality gates that support safe and fast deployments.
• Define strategies and test scoping for large, complex or high-risk initiatives, partnering early with engineers and product managers to assess risk, define coverage and challenge assumptions.
• Continuously refine testing approaches, tooling, and processes to improve speed, reliability, and confidence at scale across Nscale.
• Coach and mentor engineers and Junior SDETs on test design, automation patterns, contract testing, and quality-first development practices.
• Ensure automated tests provide high-signal feedback and integrate cleanly with CI/CD workflows, Slack notifications, and dashboards.
• Design, build, and maintain automation frameworks and test infrastructure across multiple layers, including API, contract, integration, E2E, performance, security, and resilience testing.
• Constantly push boundaries on learning and implementing the latest testing methodologies, tools and infrastructure to support initiatives where appropriate.
• Proactively monitor and surface test debt, quality gaps, and systemic risks, proposing and implementing pragmatic improvements.

NOTE: This is not a manual QA or regression testing role, nor a release gate or sign-off function, and does not involve sole ownership of feature testing while developers “throw work over the wall.”

About You (Skills / Qualifications)

• Deep experience as a Software Development Engineer in Test or in a similar QA automation role.
• Proven ability to design, build, and evolve test frameworks and infrastructure, rather than only authoring individual test cases.
• Strong software engineering skills in one or more languages such as Go, Python, Java, or TypeScript, used to build automation, tooling, and test infrastructure.
• Experience testing distributed, cloud-native systems, including APIs, event-driven architectures, and stateful workflows.
• Experience testing machine learning applications, inference services or AI-related software.
• Strong knowledge of testing methodologies, tools, and processes, including automated testing of distributed systems and APIs.
• Deep understanding of risk-based testing, test pyramid principles, and continuous quality practices in high-velocity environments.
• Comfortable operating in a developer-led quality model, where engineers own feature quality and SDETs enable scale.
• Experience with CI/CD tools and platforms (e.g., GitLab CI/CD, Jenkins, GitHub Actions).
• Experience using AI-enabled tools to improve development or testing workflows (e.g. code generation, test generation, or agent-based tooling).
• Demonstrated ability to conduct comprehensive performance and scalability testing in cloud environments.
• Experience working with cloud-native technologies such as Kubernetes and Docker.
• Ability to mentor and influence engineers on test design, automation patterns, and quality-first development practices without acting as a gatekeeper.

Nice to have

• Knowledge of monitoring and observability practices and tools (e.g., Prometheus, Grafana, Datadog).
• Experience with infrastructure-as-code tools like Terraform.
• Experience with contract testing and API schema validation, including OpenAPI or similar specifications.
• Exposure to security, chaos, load, or resilience testing in production-like environments.

What We Can Offer You

At Nscale, you'll find a collaborative, supportive, and innovative environment where your contributions spark real impact. We're building something extraordinary, and we want you at the core. Highly competitive package (base + equity) with reviews every 12 months. Join the fastest-growing tech startup, your chance to push boundaries, collaborate with brilliant minds, and make your mark on cutting-edge AI. Expect a dynamic progression plan tailored to your ambitions. Grow by trying new things, leading, challenging the status quo, and owning your impact, always with our full support.

Human-First Flexibility: We treat you as humans first. Our flexible workplace trusts Nscalers to deliver, giving you the autonomy to shape your day around life's moments. Join our thriving remote-first team. Geography is no barrier to impact or connection. We build seamless virtual collaboration, empowering you, wherever you work.

We strongly encourage applications from people of colour, the LGBTQ+ community, people with disabilities, neurodivergent people, parents, carers, and people from lower socio-economic backgrounds. If there’s anything we can do to accommodate your specific situation, please let us know.