Performance Tester (freelance)
Performance Testing | Apache JMeter | UI & API | Web & Mobile | Load/Stress/Endurance | Java Scripting | CI/CDOne of our clients is looking for a freelance Performance Tester with strong UI automation and API testing skills. The role is based in Mechelen.
They are seeking a highly experienced performance testing specialist who can design, script, execute and analyse performance tests across web, mobile and API-based applications. The ideal consultant combines strong technical expertise with a proactive mindset and excellent communication skills.Practical details:Start date: February 2026 (asap)
Duration: Outcome 2026 with possible extension (3 months confirmed)
Regime: Fulltime
Location: Mechelen
Office days: Monday & Thursday
Key Responsibilities
1. Script end‑to‑end UI user flows for web and mobile applications using Apache JMeter.
2. Design, develop and execute comprehensive performance test scenarios for web, API and mobile applications.
3. Maintain clear linkage between test scenarios, scripts and non‑functional requirements (NFRs).
4. Prepare and manage performance test data, including creation of datasets and supporting teams with data needs.
5. Work with both standalone and distributed JMeter environments, including Docker‑based setups.
6. Execute load, stress, volume and endurance tests.
7. Collect detailed technical input from developers and solution architects.
8. Build realistic workload models, gather stakeholder feedback, and obtain approval ahead of execution.
9. Produce performance test execution reports using JMeter Dashboards, including deep‑dive analysis and recommendations.
10. Use monitoring and observability tools such as Dynatrace for analysis and troubleshooting.
11. Define environmental scalability and extrapolation aligned with production environments.
12. Take ownership of performance scripts and maintain existing assets.
13. Register, track and follow up performance‑related defects with development teams.
14. Provide structured progress reporting to the Delivery Manager and maintain accurate status in Jira.
Required Skills & Experience
15. Minimum 5+ years of hands‑on performance testing experience.
16. Strong scripting skills (Java).
17. Solid experience with Apache JMeter for UI and API performance testing.
18. Strong analytical thinking, attention to detail and technical autonomy.
19. Excellent communication skills in English and Dutch.
20. Ability to work independently in a complex technical environment.
Education
21. Bachelor’s or Master’s degree in Computer Science, ICT/IT, or a related technical discipline.
Nice to Have
22. Experience in a telecommunications environment.
23. Knowledge of CI/CD pipeline integration for performance testing.
24. Familiarity with additional monitoring/performance analysis tools.
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