Production Storage Tiering: AWS S3, Azure Blob, and Google Cloud Storage

Cloud Object Storage Tiers Overview
Major cloud providers offer similar tiering structures with different names. Understanding the mapping helps translate designs across platforms. All follow the same principle: lower storage cost means higher retrieval cost and longer retrieval time. The tiers are not just marketing names but represent fundamentally different storage technologies, from SSD arrays to robotic tape libraries.
Hot and Standard Tiers
The default tier for frequent access. Storage cost around $0.023/GB/month. No retrieval fees. Access latency in milliseconds. Designed for data accessed multiple times per month. This tier uses SSD or high performance HDD storage with multiple replicas for durability. Egress fees apply when data leaves the cloud region but no per request retrieval fees. Most applications start here and tier down based on observed access patterns.
Infrequent Access Tiers
Names include Infrequent Access, Cool, and Nearline. Storage cost drops to $0.0125/GB/month. Retrieval fees around $0.01/GB. Minimum storage duration of 30 days. Access latency still in milliseconds. Designed for data accessed once per month or less. The minimum duration matters: deleting data before 30 days still incurs the full 30 day storage charge. This tier works well for backups, logs older than a week, and user content that is uploaded but rarely viewed.
⚠️ Key Trade-off: Infrequent access tiers charge per retrieval. If access patterns are unpredictable and data gets accessed more than expected, retrieval fees can exceed savings from lower storage costs.
Cold and Archive Tiers
Names include Glacier, Coldline, and Archive. Storage cost drops to $0.004/GB/month. Retrieval fees around $0.02-0.03/GB. Minimum storage duration 90-180 days. Access latency ranges from minutes to hours depending on retrieval tier. Deep archive (Glacier Deep Archive, Archive Storage) costs $0.00099/GB/month with 12 hour retrieval. These tiers use offline media like tape or spun down disks. Retrieval requires physical operations.
Lifecycle Policies
Cloud providers offer automated tiering through lifecycle policies. A policy might specify: move to Infrequent Access after 30 days, move to Glacier after 90 days, delete after 365 days. Policies apply to prefixes, tags, or entire buckets. Important: lifecycle transitions are not instant. They can take up to 24-48 hours to execute after the age threshold is met.
Intelligent Tiering Options
Some providers offer automatic tiering based on observed access patterns. Data starts in hot tier. After 30 days without access, it moves to infrequent. After 90 days, to archive. Any access moves it back to hot. This eliminates policy guesswork but adds monitoring overhead (small per object monitoring fee). Works best for unpredictable workloads where manual policy tuning is difficult. Not ideal for predictable patterns where fixed policies are more cost effective.

💡 Key Takeaways

✓Cloud tiers: Standard ($0.023/GB), Infrequent Access ($0.0125/GB with $0.01/GB retrieval), Archive ($0.004/GB with hours retrieval)

✓Minimum storage durations: 30 days for Infrequent Access, 90-180 days for Archive - early deletion still charges full duration

✓Lifecycle policies automate tier transitions based on age - transitions take 24-48 hours after threshold

✓Intelligent tiering observes access patterns automatically but adds monitoring overhead - best for unpredictable workloads

📌 Interview Tips

1When discussing cloud storage costs, explain all three cost components: storage fee, retrieval fee, and minimum duration penalties

2Describe a typical lifecycle policy: hot 30 days, infrequent access 30-90 days, archive 90-365 days, delete after 365

3Explain when intelligent tiering is better than fixed policies - unpredictable access patterns where manual tuning is difficult

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