A company needs to store objects that are frequently accessed for the first 30 days, then rarely accessed afterward. Which S3 storage class is most cost-effective?

Correct answer: S3 Standard-IA with lifecycle policy

Option D is correct because S3 Standard-IA (Infrequent Access) combined with a lifecycle policy is the most cost-effective approach: objects remain in S3 Standard during the first 30 days of frequent access, then a lifecycle rule automatically transitions them to Standard-IA, which has a lower storage cost suited to rarely accessed data with retrieval fees. Option A, S3 Glacier Instant Retrieval, is designed for data accessed only once or twice per quarter, making it too restrictive for data that is still occasionally accessed after 30 days, and it incurs higher retrieval latency concerns. Option B, S3 Intelligent-Tiering, automatically moves objects between tiers but charges a monthly monitoring and automation fee per object, which adds unnecessary cost when the access pattern is already well-known and predictable. Option C, S3 Standard, is the most expensive per-GB storage tier and is intended for frequently accessed data; keeping objects there after the 30-day period wastes money.