You have 30 microservices, each needs database credentials. Where should you store credentials for secure, centralized access?

A secret management system like Google Cloud Secret Manager is the most secure and scalable solution. It centralizes secrets, encrypts them at rest and in transit, and allows fine-grained access control with auditing. This prevents credentials from being exposed in code repositories or configuration files. Storing credentials in source code is highly insecure, as it exposes them to anyone with access to the repository. Environment variables are better than source code but still less secure than a dedicated secret manager, as they can be easily accessed by other processes on the same machine or exposed in logs. A config file with ACLs improves security over plain text, but it's still a static file that needs careful management and doesn't offer the dynamic rotation, auditing, or centralized control of a secret management system.