Location: Belgium (Mechelen)
Start Date: February 2026 (ASAP)
Contract Type: Freelance
Workload: Fulltime
Office Days: Monday & Thursday
About the Role
One of our clients is looking for a highly skilled Freelance Performance Tester with strong UI automation and API testing expertise. The role is based onsite in Mechelen. They are seeking a senior performance testing specialist capable of designing, scripting, executing, and analysing performance tests across web, mobile, and API-driven applications. The ideal consultant brings deep technical knowledge, a proactive mindset, and excellent communication skills.
Key Responsibilities
* Script end-to-end UI user flows for web and mobile applications using Apache JMeter
* Design, develop, and execute comprehensive performance test scenarios for web, API, and mobile applications
* Maintain clear traceability between test scenarios, scripts, and Non-Functional Requirements (NFRs)
* Prepare and manage performance test data, including dataset creation and supporting teams with data needs
* Work with standalone and distributed JMeter environments, including Docker-based setups
* Execute load, stress, volume, and endurance tests
* Collect detailed technical input from developers and solution architects
* Build realistic workload models, gather stakeholder feedback, and secure approval before execution
* Produce performance test execution reports using JMeter Dashboards, including deep-dive analysis and recommendations
* Use monitoring and observability tools such as Dynatrace for analysis and troubleshooting
* Define environmental scalability and extrapolation aligned with production environments
* Take ownership of performance scripts and maintain existing assets
* Register, track, and follow up on performance-related defects with development teams
* Provide structured progress reporting to the Delivery Manager and maintain accurate status in Jira
Required Skills & Experience
* Minimum 5+ years of hands-on performance testing experience
* Strong scripting skills (Java)
* Solid experience with Apache JMeter for UI and API performance testing
* Strong analytical mindset, attention to detail, and technical autonomy
* Excellent communication skills in English and Dutch
* Ability to work independently in a complex technical environment
Education
* Bachelor's or Master's degree in Computer Science, ICT/IT, or a related technical field
Nice to Have
* Experience in a telecommunications environment
* Knowledge of CI/CD pipeline integration for performance testing
* Familiarity with additional monitoring or performance analysis tools