Implementing a Key Management Service (KMS) can present several challenges. One common challenge is ensuring integration with existing systems and workflows, as it requires compatibility with various applications and data storage solutions. Additionally, managing access control and permissions effectively is crucial to ensure that only authorized individuals can access or use the encryption keys. Another challenge is maintaining compliance with regulatory requirements, which can vary depending on industry and region. Organizations must also address potential performance impacts, as encryption and decryption operations can affect system speed and efficiency. Finally, the cost of implementing and maintaining a KMS, especially for large-scale operations, can be significant and needs to be factored into the overall IT budget.