Amazon S3 (Simple Storage Service)

Amazon Simple Storage Service (S3) is an object storage service that offers industry-leading scalability, data availability, security, and performance. It is one of the oldest and most widely used AWS services.

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What Is Object Storage?

Unlike block storage (hard drives) or file storage (NFS), object storage stores data as discrete objects. Each object contains:

• Data — the file itself (image, video, log, backup, etc.)
• Metadata — information about the object (size, date, content type, custom tags)
• Key — a unique identifier within the bucket

You access objects via HTTP/HTTPS using a URL like: https://my-bucket.s3.amazonaws.com/photos/sunset.jpg

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Core Concepts

Buckets

A bucket is a container for objects. Think of it like a top-level folder.

• Bucket names must be globally unique across all AWS accounts
• Buckets are created in a specific region
• There is no limit on the number of objects in a bucket

Objects

An object is any file stored in S3.

• Maximum object size: 5 TB
• Single upload limit: 5 GB (use multipart upload for larger files)
• Each object has a key (the full path within the bucket)

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Storage Classes

S3 offers multiple storage classes to optimise cost based on access patterns:

Storage Class	Use Case	Availability	Min Duration
S3 Standard	Frequently accessed data	99.99%	None
S3 Intelligent-Tiering	Unknown or changing access patterns	99.9%	None
S3 Standard-IA	Infrequently accessed, rapid retrieval	99.9%	30 days
S3 One Zone-IA	Infrequent, non-critical, recreatable data	99.5%	30 days
S3 Glacier Instant Retrieval	Archive with instant access	99.9%	90 days
S3 Glacier Flexible Retrieval	Archive, retrieval in minutes to hours	99.99%	90 days
S3 Glacier Deep Archive	Long-term archive, retrieval in hours	99.99%	180 days

Lifecycle Policies

You can create rules to automatically transition objects between storage classes or delete them after a specified period.

Example lifecycle rule:

• After 30 days → move to S3 Standard-IA
• After 90 days → move to S3 Glacier Flexible Retrieval
• After 365 days → delete

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Versioning

S3 versioning keeps multiple variants of an object in the same bucket. When enabled: