S3 is AWS object storage. It stores files as objects inside buckets.

Object storage

S3 is not a normal filesystem and not a relational database. It is designed for storing objects like:

• Images.
• Videos.
• Logs.
• Backups.
• Static website files.
• Data exports.
• User uploads.

Each object has data, metadata, and a key.

Buckets and keys

A bucket is the top-level container. An object key is the object's path-like name.

Example:

bucket: learning-atlas-uploads
key: users/42/avatar.png

S3 keys look like folders, but they are object names.

Access control

By default, keep buckets private.

Common access patterns:

• Backend uploads files using IAM permissions.
• Users download files through signed URLs.
• Static public assets use controlled public access or CDN.
• CloudFront serves private S3 content through an origin access control.

Avoid making a whole bucket public unless there is a clear reason.

Versioning

S3 versioning keeps previous versions of objects.

It helps recover from:

• Accidental deletion.
• Bad overwrite.
• Some ransomware-style damage.

Versioning can increase storage cost, so lifecycle rules matter.

Lifecycle rules

Lifecycle rules can move or delete objects automatically.

Examples:

• Delete temporary uploads after 7 days.
• Move old logs to cheaper storage.
• Expire old object versions.

Backend use cases

• Upload user files.
• Store generated reports.
• Keep application backups.
• Serve static assets.
• Store logs and event archives.

Quick revision

• S3 stores objects inside buckets.
• Object keys identify files.
• Keep buckets private by default.
• Use signed URLs for controlled access.
• Versioning and lifecycle rules help manage safety and cost.