GCP database access security is not something you bolt on after launch. In production, every credential, role, and connection path must be locked down. Start with Identity and Access Management (IAM). Give each engineer the minimum roles to do their job. Use service accounts, not user accounts, for applications. Audit them regularly.
When debugging in production, avoid giving blanket access to the database. Instead, route through secure debugging tools that honor IAM policies. Enable Cloud SQL IAM database authentication to tie access directly to Google identities. Combine this with private IP connections so traffic never leaves the VPC.
For fine-grained control, implement row-level or column-level security where supported. In GCP, this can be enforced inside BigQuery using authorized views, or inside Cloud Spanner with custom logic. Every change should pass a review. Every debug session must be traceable.