Senior Performance Test Engineer

CSHARK is a company located in Wrocław offering international projects where this role is responsible for performance testing.

• Strong hands-on experience with performance testing and independently driving testing activities end to end.
• Strong practical knowledge of k6 scripting, checks, metrics, and thresholds.
• Solid understanding of k6 workload models and executors, including VU-based and arrival-rate-based approaches.
• Good working knowledge of JavaScript (ES modules) for modular test scripts.
• Strong experience testing REST APIs including HTTP methods, headers, session-token authentication, and data correlation.
• Ability to interpret HTTP and application-level error codes and identify sources of test failures.
• Hands-on experience with Azure DevOps Pipelines including running and parameterizing tests, variables, conditions, artifacts, and agents.
• Practical experience with Prometheus and Grafana for performance metric analysis and correlation.
• Experience preparing and validating test data for performance testing.
• Ability to translate business requirements into meaningful performance scenarios and acceptance criteria.
• Strong analytical skills to identify bottlenecks, performance ceilings, and distinguish degradation types.
• Strong troubleshooting skills to differentiate between script, data, application, infrastructure, and environment issues.
• Experience producing clear reports and evidence-based recommendations without overinterpretation.
• Ability to take ownership of the performance-testing area and coordinate activities across multiple teams.
• Practical experience using AI tools to support testing activities with critical validation.
• Basic knowledge of Git and feature-branch workflows.
• Strong written and spoken English at C1 level for international communication.

• Owning performance testing end to end — from requirements gathering and test-data preparation to execution, analysis, and reporting.
• Designing performance scenarios based on business requirements, including transactions per hour, load tiers, and acceptance criteria.
• Building and maintaining performance test scripts using k6 and JavaScript.
• Selecting appropriate k6 workload models and executors for different scenarios.
• Testing REST API flows including authentication, sessions, and data correlation.
• Preparing and validating test data, including CSV feeders and sensitive data.
• Running and parameterizing performance tests through Azure DevOps Pipelines.
• Exporting and analyzing performance metrics using Prometheus and Grafana.
• Correlating client-side test results with application and infrastructure metrics.
• Identifying bottlenecks, practical performance ceilings, and root causes of failures.
• Distinguishing between script, test-data, application, infrastructure, and environment issues.
• Preparing clear performance reports and evidence-based recommendations for technical and non-technical stakeholders.
• Identifying risks and blockers early and proposing mitigation measures.
• Coordinating performance-testing activities across Development, DevOps, QA, and business teams.
• Using AI tools to support script development, test-data preparation, log and result analysis, and reporting while critically validating outputs.

Candidates consent to personal data processing for recruitment by CSHARK Sp. z o.o. located in Wrocław under GDPR and related laws. Data may be stored on servers in the European Economic Area and transferred under standard clauses. Data subject rights and legal notices are provided. Data provision is obligatory for contractual agreements and recruitment participation.