Senior Software Engineer – Performance Engineer

Job Description

WHAT YOU’LL DO

As a Senior Software Engineer – Performance Engineer at H&M Business Tech, you’ll play a key part in ensuring the performance, scalability, and resilience of H&M’s large-scale system landscape, from Front End platforms and web applications to API backends and smaller in-house applications. You’ll design and execute load, stress, soak, and spike tests across modern microservice architectures using tools like k6 and LoadRunner (or similar).

Key Responsibilities

Your key responsibilities will include:

• Developing and maintaining scalable performance testing frameworks that enable product teams to design, execute, and analyse performance tests independently.
• Defining NFRs, SLAs/SLOs, workloads, volumes, success criteria, and performance objectives with product and engineering teams.
• Building internal tools and AI-driven solutions to automate test orchestration, analysis, and reporting.
• Designing and executing load, stress, spike, and soak tests, including scenario modelling, correlation, parameterization, and test-data management.
• Leading root-cause analysis and troubleshooting across HTTP/API, application, database, cloud, Kubernetes, and infrastructure layers.
• Conducting change impact and performance risk assessments for new features, architectural changes, and releases.
• Using Splunk, Dynatrace, and other observability tools to monitor services, analyse performance, and create dashboards and alerts.
• Collaborating with platform and cloud teams to optimize AKS, KEDA, infrastructure capacity, and overall system performance.
• Supporting capacity forecasting, resilience testing, synthetic monitoring, and distributed load testing where appropriate.
• Producing test reports, executive summaries, recommendations, risk assessments, and Go/No-Go recommendations.
• Defining and continuously improving performance engineering standards, frameworks, and governance across product teams.
• Connecting performance insights to customer journeys, business KPIs, and product outcomes.
• Coaching and mentoring engineers to build performance engineering capability within product teams.

WHO YOU’LL WORK WITH

At H & M you’ll be with the Digital Foundation area which is integral part of the Commercial Tech Domain. This area builds on the existing Product Operations and Online Applications units, reflecting the organization’s evolution toward a more integrated digital capability and focusing on enabling teams to deliver with excellence. Delivery Foundation - Providing a mixture of niche platform SMEs, e.g. traffic flow optimization, platform vendor management and enabling support to teams both in area and wider on core NFRs topics.
You’ll be part of a global, cross-functional team focused on enabling data driven decision making at the core of our customer offering. Our mission is to empower assortment teams to efficiently and accurately plan and adjust demand for articles across all markets and touchpoints, with the flexibility to swiftly adapt to changing circumstances.

WHO YOU ARE

We are looking for people with…

• 6+ years of experience in performance or reliability engineering within high-traffic, distributed systems.
• Strong experience in NFR definition, workload modelling, SLA/SLO definition, and performance requirements gathering.
• Hands-on expertise with k6, JMeter, LoadRunner, or similar performance testing tools.
• Strong understanding of APIs, microservices, databases, event-driven systems, networking, and cloud-native architectures.
• Proven ability to troubleshoot complex performance and reliability issues across the technology stack.
• Strong Python, Bash, JavaScript, or similar scripting and automation skills.
• Experience with Git, CI/CD, and automated performance testing/gates.
• Experience with Splunk, Dynatrace, SignalFx, or comparable observability tools.

Nice to have:

• Strong collaborators who can connect technical performance work to product and business outcomes and communicate effectively with diverse stakeholders.
• Experienced in coaching and mentoring engineers, building high-performing autonomous teams, and fostering accountability and continuous improvement.
• Proactive in challenging existing approaches and driving improvements in performance engineering maturity, scalability, and reliability.
• Comfortable working across cloud, Kubernetes/AKS, CDN/caching, APIs, microservices, and observability environments…