You have deployed an application that needs to encrypt data before writing to a database.

Comprehensive and Detailed in Depth Explanation:

For encrypting data before writing it to a database, theTransitsecrets engine is the appropriate choice. The HashiCorp Vault documentation describes it as handling "cryptographic functions on data in-transit" and notes that it "can be viewed as 'cryptography as a service' or 'encryption as a service.'" It is designed to encrypt data without storing it, making it ideal for applications needing to secure data before storage in an external database. The primary use case is "to encrypt data from applications while still storing that encrypted data in some primary data store."

TheSSHsecrets engine manages SSH keys and authentication, not data encryption. ThePKIsecrets engine handles certificate management, not general data encryption. TheTOTPsecrets engine generates time-based one-time passwords, unrelated to data encryption. Thus, Transit is the correct choice.