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Agent guide: [/agents.md](https://www.wearedevelopers.com/agents.md). --- # Software Development Engineer in Test III - **Company:** Número De - **Location:** Madrid, Spain - **Salary:** €60,000.0 - €90,000.0 - **Contract:** Permanent contract - **Skills:** Clean Code Principles, Amazon Web Services, Application Performance Management, Automation of Tests, Continuous Integration, DevOps, Python (Programming Language), Load Testing, Reliability Engineering, Software Deployment, Software Engineering, Software Systems, Systems Architecture, Systems Integration, TypeScript, Pulumi, Google Cloud, Performance Testing, Delivery Pipeline, Build Management, Infrastructure Automation Frameworks, Low Latency, Production Code, Cloudflare, Software Coding, Terraform, SDET, Programming Languages - **Published:** September 27, 2026 - **Apply:** https://www.adzuna.es/contact-us.html ## About the Role + Strong professional software engineering experience with the ability to independently design, build, and maintain software systems + Strong coding skills in TypeScript, Python, or comparable modern programming languages + Experience building automated testing systems, engineering tooling, testing infrastructure, or similar software-driven quality solutions + Hands-on experience with load testing, performance testing, stress testing, synthetic testing, or large-scale application validation + Experience working with applications or platforms serving millions of users or visitors, ideally at multi-million or tens-of-millions scale + Experience working with cloud-hosted applications and infrastructure using AWS, Google Cloud, Cloudflare, or comparable platforms + Strong understanding of DevOps, platform engineering, infrastructure, scalability, and modern software deployment practices + Experience with CI/CD and integrating automated validation into continuous integration and deployment workflows + Experience with Infrastructure as Code using Terraform, Pulumi, or similar technologies + Strong understanding of application performance concepts including latency, bandwidth, throughput, scalability, reliability, and infrastructure optimization + Ability to independently investigate complex technical problems and build solutions with limited oversight + Strong written and spoken English with the ability to communicate technical decisions and collaborate effectively with a distributed engineering team Preferred + Experience supporting globally distributed applications serving tens of millions of monthly visitors + Experience with high-traffic e-commerce platforms or other large-scale consumer-facing applications + Experience working with custom or internally built platforms rather than primarily testing third-party or off-the-shelf software + Experience optimizing applications or infrastructure where speed, latency, bandwidth, and infrastructure cost are critical considerations + Experience building testing infrastructure or frameworks from the ground up rather than primarily working within established QA systems + Background in DevOps, Site Reliability Engineering, Platform Engineering, performance engineering, or infrastructure engineering + Experience working in fast-moving startup or lean engineering environments where engineers have significant ownership and autonomy ## Description As a Senior Software Development Engineer in Test (SDET), you will build the systems, infrastructure, and tooling that enable a high-scale technology platform to test applications under conditions that closely replicate the real world. This is an engineering role, not a traditional manual QA position. You will write production-quality code and build testing platforms capable of validating performance, reliability, and scalability across applications serving millions of users globally. A key challenge will be creating environments and systems that can simulate traffic and workloads that are difficult to reproduce through conventional testing environments. You will work closely with platform engineers and the broader engineering organization to give the team confidence that new code and infrastructure will perform reliably when deployed at scale. This role is ideal for an engineer who enjoys solving complex infrastructure, performance, and reliability problems and is comfortable independently designing solutions from the ground up. Responsibilities + Design and build scalable testing systems, platforms, and infrastructure that replicate real-world production conditions + Develop software and tooling to test application performance, reliability, scalability, and infrastructure behavior at high traffic volumes + Build and maintain load, performance, stress, and synthetic testing capabilities for applications serving millions of users globally + Create testing environments and processes that provide confidence that new code and infrastructure will scale successfully in production + Write high-quality code using TypeScript, Python, or similar languages to build testing tools, automation, and supporting systems + Design tests that identify performance bottlenecks related to latency, bandwidth, application speed, infrastructure capacity, and resource utilization + Integrate automated testing and quality validation into CI/CD pipelines and engineering workflows + Work with cloud-hosted applications and infrastructure across platforms such as AWS, Cloudflare, Google Cloud, or similar providers + Use Infrastructure as Code tools such as Terraform, Pulumi, or equivalent technologies to support repeatable and scalable testing environments + Partner closely with platform engineers to understand system architecture, production behavior, and infrastructure constraints + Analyze test results and production-like workloads to identify scalability risks before changes reach real-world traffic + Help establish the technical standards, systems, and processes for a new engineering-focused testing function ## Related Videos - [Navigating the Corporate Jungle: Life as a Developer in a large Company](https://www.wearedevelopers.com/videos/621-navigating-the-corporate-jungle-life-as-a-developer-in-a-large-company) - [Why segmenting your infrastructure into tiers makes your infrastructure design better](https://www.wearedevelopers.com/videos/1960-why-segmenting-your-infrastructure-into-tiers-makes-your-infrastructure-design-better) - [Shifting Stress to Progress— Understanding DevOps to do DevOps Better](https://www.wearedevelopers.com/videos/268-shifting-stress-to-progress-understanding-devops-to-do-devops-better) - [Testing .NET applications a Tool box for every developer](https://www.wearedevelopers.com/videos/704-testing-net-applications-a-tool-box-for-every-developer) - [Unleashing Potential Across Teams: The Power of Infrastructure as Code](https://www.wearedevelopers.com/videos/930-unleashing-potential-across-teams-the-power-of-infrastructure-as-code) - [From DevOps to Scaled DevOps: How We’re Rebuilding Continuous Delivery as a Platform](https://www.wearedevelopers.com/videos/100018-from-devops-to-scaled-devops-how-we-re-rebuilding-continuous-delivery-as-a-platform) ## Related Articles - [The 8 Best Code Testing Tools](https://www.wearedevelopers.com/magazine/402-the-8-best-code-testing-tools) - [The 12 Best Jobs for Software Engineers](https://www.wearedevelopers.com/magazine/401-the-12-best-jobs-for-software-engineers) - [Is Software Engineering Over-Saturated?](https://www.wearedevelopers.com/magazine/418-is-software-engineering-over-saturated) - [Fully Remote Software Engineer Jobs](https://www.wearedevelopers.com/magazine/447-fully-remote-software-engineer-jobs) - [Is Software Engineering Hard?](https://www.wearedevelopers.com/magazine/448-is-software-engineering-hard) - [Top-Paying Tech Jobs (with Salaries)](https://www.wearedevelopers.com/magazine/372-top-paying-tech-jobs-with-salaries)