Senior Performance Test Engineer

Quick Facts

Senior Performance Test Engineer responsible for performance testing end to end in an international project.

Description

You will drive performance testing from understanding business requirements and defining workload models through preparing test data and k6 scripts, test execution, results analysis, and final recommendations.

More than running tests: you must interpret results to determine the practical performance ceiling, identify bottlenecks, and distinguish infrastructure issues from application errors, test-data problems, or issues within the test scripts.

You will work with k6, JavaScript, Azure DevOps, Prometheus, and Grafana and collaborate across Development, DevOps, QA, and business teams, working closely with the Project Manager and Release Manager while taking ownership of the performance testing area.

Benefits

• Work remotely or from offices in Wroclaw or Bielsko-Biala (occasional visits may be needed)
• Adjustable working hours, starting between 7:00 and 10:00 am
• Work with the latest technologies and international clients
• TechTalks, meet-ups, and guilds for knowledge exchange
• Close-knit team with regular integrations
• Flat structure
• Bonuses for employee referrals (from 3000 PLN to 7000 PLN)

Role & Responsibilities

• Own performance testing end to end: requirements, test-data preparation, execution, analysis, and final reporting
• Design performance scenarios based on business requirements (transactions per hour, load tiers, acceptance criteria)
• Build and maintain performance test scripts using k6 and JavaScript
• Select appropriate k6 workload models and executors for different performance scenarios
• Test REST API flows, including authentication, sessions, and data correlation between steps
• Prepare and validate test data, including CSV feeders and sensitive data
• Run and parameterise performance tests through Azure DevOps Pipelines
• Export and analyse performance metrics using Prometheus and Grafana
• Correlate client-side test results with application and infrastructure metrics
• Identify bottlenecks, practical performance ceilings, and root causes of failures
• Distinguish between script, test-data, application, infrastructure, and environment issues
• Prepare clear performance reports and evidence-based recommendations for technical and non-technical stakeholders
• Identify risks and blockers early and propose appropriate mitigation
• Coordinate performance-testing activities across Development, DevOps, QA, and business teams
• Use AI tools to support script development, test-data preparation, log and result analysis, and reporting with critical validation

Requirements

• Strong hands-on experience with performance testing and independently driving performance-testing activities end to end
• Strong practical knowledge of k6 (scripting, check(), metrics, thresholds)
• Solid understanding of k6 workload models and executors (VU-based vs arrival-rate-based approaches)
• Good working knowledge of JavaScript (ES modules) for modular test scripts
• Strong experience testing REST APIs (HTTP methods, headers, session-token authentication, data correlation between requests)
• Ability to interpret HTTP and application-level error codes and identify the actual source of performance-test failures
• Hands-on experience with Azure DevOps Pipelines (run/parameterise tests, variables, conditions, artifacts, dedicated agents/pools)
• Practical experience with Prometheus and Grafana (metrics analysis and correlation)
• Experience preparing and validating test data for performance testing
• Ability to translate business requirements into performance scenarios, workload models, and acceptance criteria
• Strong analytical skills to identify bottlenecks and determine practical performance ceilings, distinguishing degradation from hard performance breaks
• Strong troubleshooting skills to distinguish between script, data, application, infrastructure, and environment issues
• Experience producing clear performance reports and evidence-based recommendations without overinterpreting results
• Ability to take ownership of the performance-testing area and coordinate across multiple teams and dependencies
• Practical experience using AI tools to support performance-testing activities with critical validation of AI-generated output
• Basic knowledge of Git and feature-branch workflows
• Strong written and spoken English for international cross-functional collaboration