You are managing a small Cloud SQL instance for developers to do testing. The instance is not critical and has a recovery point objective (RPO) of several days. You want to minimize ongoing costs for this instance. What should you do?

The primary goal is to minimize ongoing costs for a non-critical test instance with a relaxed Recovery Point Objective (RPO) of several days. Enabling automated backups provides a daily recovery point, which satisfies the RPO. The most effective way to reduce costs, beyond the instance size itself, is to disable features that are not needed. Transaction logs (binary logs in MySQL or write-ahead logs in PostgreSQL) are required for point-in-time recovery (PITR). Since the RPO is several days, the precision of PITR is unnecessary. Disabling transaction log retention eliminates the associated storage costs, directly addressing the goal of cost minimization while still meeting the recovery requirements.

A. Taking no backups completely violates the stated RPO of several days. In case of failure, all data would be lost, which is unacceptable even for a test instance with a relaxed RPO.
B. While manual backups meet the RPO, they introduce operational overhead. The automated backup feature is a managed, simpler, and more reliable way to achieve a daily backup schedule.
D. Turning on transaction log retention enables point-in-time recovery, which incurs additional storage costs. This feature is not required to meet an RPO of several days and contradicts the primary goal of minimizing costs.

1. Google Cloud Documentation - Cloud SQL - Backups overview: "To use point-in-time recovery, you must enable automated backups and binary logging (for MySQL) on your instance." This establishes the link between transaction logs (binary logging) and the unnecessary point-in-time recovery feature for this scenario.

2. Google Cloud Documentation - Cloud SQL - Tips for working with backups: Under the "Cost" section, it states, "To reduce costs, you can disable binary logging when you don't need point-in-time recovery." This directly supports the chosen answer as the most cost-effective solution that meets the requirements.

3. Google Cloud Documentation - Cloud SQL Pricing - Backup storage: "Transaction log storage is the amount of space your transaction logs use for point-in-time recovery." This pricing detail confirms that transaction logs are a separate and additional cost specifically for PITR, which should be avoided to minimize costs in this scenario.