Introduction to Amazon S3

This section is very important because Amazon S3 is one of the main building blocks of AWS.
Amazon S3 is advertised as infinitely scaling storage.
A lot of the web relies on Amazon S3.
Many websites use S3 as a backbone.
Many AWS services also use Amazon S3 for integrations.

Use Cases for Amazon S3

Backup and storage (for your files, disks, etc.)
Disaster recovery: You can move your data to another region in case one goes down.
Archival purposes: Archive files and retrieve them later at a much cheaper cost.
Hybrid cloud storage: Extend on-premises storage to the cloud using S3.
Application hosting
Media hosting: Store video files, images, and more.
Data lake storage for big data analytics.
Software delivery: Deliver software updates via S3.
Static website hosting

Nasdaq stores 7 years of data in the S3 Glacier service (Amazon S3’s archival option).
Sysco runs analytics and gains business insights from Amazon S3.

S3 stores files (called objects) into buckets.
Buckets can be seen as top-level directories.
Files in S3 buckets are called objects.
Buckets are created in your AWS account and must have a globally unique name.
That means the name must be:
- Unique across all your regions and
- Across all AWS accounts globally.
This is the only resource in AWS that must be globally unique.
Buckets are defined at the region level.

🔸 Important Note:
Even though the bucket name is globally unique, each bucket is created in a specific AWS region.

Bucket: my-bucket  
Key: my_file.txt  
Path: s3://my-bucket/my_file.txt

so if you look into the example above,my-bucket is the top level directory (as we discussed earlier), then the key of the file at TXT is my_file.txt
In case if you want to nest into folders, then the key is going to be full path as shown below in the example

Full path is : s3//:my-bucket/my_folderI/another_folder/my_file.txt, so the key is: my_folderI/another_folder/my_file.txt
```
Key: my_folder1/another_folder/my_file.txt  
Prefix: my_folder1/another_folder/  
Object Name: my_file.txt
```
key = prefix name + Object Name (remember that object name is usually the file name at the end, rest all is prefix)
Even if it looks like folders, S3 does not have a real concept of directories.
In the UI, it might look like folders, but everything is actually a key.
Keys are just long strings that may contain slashes (/), and they are composed of a prefix and an object name.

🔸 If the file is larger than 5 GB, you must use multi-part upload to upload it in parts.

There are two types of metadata:

You can also add tags to an object:
- Tags are Unicode key-value pairs, up to 10 per object
- Useful for security, lifecycle rules, and organization