Answer: Amazon S3

## Explanation **Amazon S3 is the most cost-effective solution** for this scenario because: 1. **Long-term retention requirements**: The logs must be retained for 7 years. Amazon S3 offers lifecycle policies and storage classes (like S3 Glacier Deep Archive) that are specifically designed for long-term archival storage at very low costs. 2. **Concurrent access requirements**: The reporting tool needs to access all files concurrently. Amazon S3 provides highly available, scalable object storage that can serve multiple concurrent requests without performance degradation. 3. **Cost-effectiveness**: - **Amazon EBS**: Block storage attached to EC2 instances, not designed for long-term archival or concurrent access from multiple sources. More expensive for long-term storage. - **Amazon EFS**: File system storage that supports concurrent access, but more expensive than S3 for long-term archival purposes. - **Amazon EC2 instance store**: Ephemeral storage that is lost when instances are stopped/terminated - completely unsuitable for 7-year retention. - **Amazon S3**: Object storage with tiered pricing (Standard, Intelligent-Tiering, Glacier, Glacier Deep Archive) that can significantly reduce costs for infrequently accessed data over 7 years. 4. **Compliance features**: S3 offers features like versioning, object lock, and compliance controls that help meet regulatory requirements. 5. **Scalability**: S3 automatically scales to handle any amount of data and concurrent access patterns. **Recommended implementation**: - Store logs in S3 Standard for initial access - Use S3 Lifecycle policies to transition objects to S3 Glacier Deep Archive after a specified period - Use S3 Select or Athena for querying log data directly from S3 - Ensure proper IAM policies for secure access This approach provides the lowest cost while meeting all requirements: 7-year retention, concurrent access, and compliance needs.

Author: LeetQuiz Editorial Team