Plaid's journey to creating a key management system was driven by the need for scalability, cost efficiency, self-serve capabilities, and operational excellence. The Security team aimed to enable the business by managing risk in an efficient and proactive manner. Building an internal Key Management System (Plaid KMS) addressed challenges unique to Plaid, such as scalability, cost efficiency, and self-serve requirements. Plaid KMS uses gRPC for inter-service communication, YAML files for access control configurations, and an SQL database for long-term cryptographic keys. The system has undergone significant operational improvements, including dedicated resources, workload segregation, and optimized API usage. Migration to the new system was complex but essential, requiring close collaboration between service owners and the Security Team. Plaid KMS is now one of the highest-traffic services at Plaid, operating with high-reliability standards and serving as a critical component for protecting sensitive data. The team has learned that ownership is ongoing, migration takes time and strategy matters, and their next focus is extending its capabilities to further secure their data lakehouse.