Understanding the S3 Consistency Model

Introduction: Consistency in S3

Amazon S3 now provides strong consistency for all read-after-write, list, and overwrite operations. This consistency model improves data reliability, especially for applications that rely on real-time data access. With strong consistency, changes are immediately visible across all S3 clients after a PUT, GET, or LIST operation.

Tip: S3 Bucket Name Generator - Use this tool to generate unique and compliant S3 bucket names.

Strong Consistency Examples

1. GET after PUT:

   • When you upload an object with PUT, a subsequent GET request immediately retrieves the new data.
   • Example:
     • PUT a file to S3.
     • Follow with GET to fetch it.
     • Result: The latest version is retrieved immediately.

2. GET after DELETE:

   • Once an object is deleted, a subsequent GET request will reflect the deletion immediately.
   • Example:
     • DELETE an object from S3.
     • Follow with GET for the same object.
     • Result: 404 Not Found, confirming deletion.

3. LIST after PUT or DELETE:

   • Listing (e.g., LIST objects in a bucket) reflects any recent PUT or DELETE actions.
   • Example:
     • Upload or delete multiple files.
     • Immediately run LIST in the bucket.
     • Result: LIST displays the updated contents.

Conclusion: Enhanced Reliability with Strong Consistency

S3’s strong consistency eliminates the need for workarounds, offering real-time, reliable data access across all applications. This improvement is particularly useful in scenarios where immediate consistency is critical, such as event processing, real-time analytics, and content delivery.