The article explores the implementation of pseudonymization techniques for protecting Personal Data as defined by the General Data Protection Regulation (GDPR), focusing primarily on data ingestion into Elasticsearch using Logstash. Pseudonymization is highlighted as a GDPR principle for securing Personal Data, allowing organizations to maintain operational capabilities while reducing protection costs compared to leaving data intact. The article distinguishes pseudonymous data from anonymous data, emphasizing that pseudonymized data still allows for potential re-identification if additional information is available, thereby requiring appropriate security measures. It details the use of hashing methods, such as SHA256, and key management strategies to create and store pseudonymized data in a secure identity store, ensuring that original data can be re-associated when necessary. The article also cautions about the potential risks of hash reversal and the importance of managing keys and secrets securely, suggesting periodic key rotation to bolster security. Future discussions are anticipated to cover the reversal of pseudonymized data at scale and the tagging of Personal Data during and after ingestion, with a focus on maintaining data utility for analysis while complying with GDPR requirements.