S3 Storage Class

📦 What is a Storage Class in S3?

An S3 Storage Class defines how your data is stored, in terms of:

• Availability

• Durability

• Access frequency

• Cost

✅ Storage class is set per object, not per bucket.

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🧾 All S3 Storage Classes — Comparison Table

Storage Class	Use Case	Durability	Availability	Min Storage	Retrieval Fee	Key Notes
Standard	General-purpose storage (frequently accessed)	99.999999999% (11 9s)	99.99%	None	❌ No	Default class
Intelligent-Tiering	Unknown or variable access patterns	99.999999999%	99.9–99.99%	30 days	❌ No	Auto-moves to lower tiers
Standard-IA	Infrequent but rapid access	99.999999999%	99.9%	30 days	✅ Yes	128 KB min object size
One Zone-IA	Infrequent + non-critical data	99.999999999%	99.5%	30 days	✅ Yes	Stored in one AZ only
Glacier Instant Retrieval	Archival with millisecond access	99.999999999%	99.9%	90 days	✅ Yes	Cost-efficient alternative to Standard-IA
Glacier Flexible Retrieval	Archival, access within minutes-hours	99.999999999%	Varies	90 days	✅ Yes	Cheaper, restore in 1 min – 12 hrs
Glacier Deep Archive	Long-term archive (tapes replacement)	99.999999999%	Varies	180 days	✅ Yes	Cheapest — restore takes 12–48 hours
Reduced Redundancy (RR)	❌ Deprecated	Lower	Lower	—	❌ No	Use only for legacy cases

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🧠 When to Use Each Storage Class

Use Case	Best Class
Frequently accessed web content	Standard
User-generated content (access varies)	Intelligent-Tiering
Backups / logs accessed monthly	Standard-IA
Non-critical backup (test environments)	One Zone-IA
Compliance archives (PDFs, logs, backups)	Glacier Deep Archive
Emails or reports accessed quarterly	Glacier Flexible Retrieval

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🔄 Lifecycle Policy (Automatic Transition)

You can automatically move data between classes using lifecycle rules.

Example: Standard → IA → Glacier

{
  "Rules": [{
    "ID": "TransitionToIA",
    "Filter": { "Prefix": "" },
    "Status": "Enabled",
    "Transitions": [
      {
        "Days": 30,
        "StorageClass": "STANDARD_IA"
      },
      {
        "Days": 90,
        "StorageClass": "GLACIER"
      }
    ]
  }]
}

✅ Use this to optimize storage cost over time.

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🧪 Terraform Example: S3 with Storage Class Lifecycle

resource "aws_s3_bucket" "example" {
  bucket = "yuva-storage-demo"
}

resource "aws_s3_bucket_lifecycle_configuration" "lifecycle" {
  bucket = aws_s3_bucket.example.id

  rule {
    id     = "lifecycle-transition"
    status = "Enabled"

    transition {
      days          = 30
      storage_class = "STANDARD_IA"
    }

    transition {
      days          = 90
      storage_class = "GLACIER"
    }

    expiration {
      days = 365
    }
  }
}

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💰 Cost Consideration Summary

Cost Component	Applies to...
Storage cost (per GB)	Based on class (Glacier < IA < Standard)
PUT request	Every transition creates a PUT request
Retrieval cost	Glacier, IA, etc.
Early deletion penalty	IA/Glacier (<30/90 days)

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🔐 Encryption & Storage Class

Storage class has no impact on encryption — you can use:

• SSE-S3 (default)

• SSE-KMS

• SSE-C

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✅ TL;DR Cheat Sheet

Storage Class	When to Use	Retrieval Time
Standard	Frequently accessed files	Immediate
Intelligent-Tiering	Access pattern unknown	Immediate
Standard-IA	Infrequent access, high durability	Immediate
One Zone-IA	Non-critical backup, cheaper	Immediate
Glacier Instant	Fast-access archive	Milliseconds
Glacier Flexible	Long-term storage	1–12 hours
Glacier Deep Archive	Compliance/rarely used archive	12–48 hours

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