Answer: Coldline Storage

## Explanation For retaining audit logs for 3 years at the lowest cost, **Coldline Storage** is the correct choice. Here's why: ### Storage Class Comparison: 1. **Cloud Logging only** - Not suitable for long-term retention as logs in Cloud Logging have limited retention periods (default 30 days, configurable up to 365 days for some log types). 2. **Nearline Storage** - Designed for data accessed less than once a month, with 30-day minimum storage duration. 3. **Coldline Storage** - Designed for data accessed less than once a year, with 90-day minimum storage duration and the lowest storage costs for long-term retention. 4. **Pub/Sub** - A messaging service, not a storage solution for long-term retention. ### Cost Analysis: - **Coldline Storage** has the lowest storage costs among Google Cloud's storage classes for data that needs to be retained for years. - For 3-year retention, Coldline Storage provides the most cost-effective solution. ### Compliance Considerations: - Audit logs often have regulatory requirements for long-term retention. - Coldline Storage provides durable, secure storage with appropriate access controls for compliance purposes. ### Best Practice: Export audit logs from Cloud Logging to Cloud Storage using a Coldline Storage bucket for long-term retention at minimal cost.

Author: Rodrigo Sales