A device and method for analyzing a performance of an n-tier application capable of carrying out on-the-fly anonymization processing of production data. The production data is generated following a performance test request message transmitted to the n-tier application. The anonymization processing is implemented by an anonymization module that identifies, from a sensitive data identification repository, data to be anonymized in the response message. The anonymization processing also includes generating, from an anonymization repository, anonymized data from the previously identified data to be anonymized, and generating an anonymized response message from the anonymized data and the response message.