Read-After-Write consistency in S3

Amazon S3 provides strong read-after-write consistency for new objects and overwritten objects. This means that after a successful write of a new object or an overwrite of an existing object, any subsequent read request will immediately receive the latest version of the object.

Some key points about the consistency model of Amazon S3:

  1. Strong Read-After-Write Consistency: S3 automatically delivers strong read-after-write consistency without any changes to performance or availability, and without sacrificing regional isolation for applications.

  2. Consistent Listing Operations: S3 also provides strong consistency for list operations, so after a write, you can immediately perform a listing of the objects in a bucket with any changes reflected.

  3. Durability and Availability: The S3 Standard storage class is designed for 99.99% availability, while other storage classes like S3 Standard-IA, S3 Intelligent-Tiering, and S3 Glacier Instant Retrieval are designed for 99.9% availability. All S3 storage classes are backed by the Amazon S3 Service Level Agreement.


The strong read-after-write consistency provided by Amazon S3 helps in the following ways:

  1. Immediate Data Availability: When you write a new object or overwrite an existing object in S3, you can immediately read the latest version of the object. This ensures that your applications always see the most up-to-date data, without having to worry about eventual consistency.

  2. Reliable Data Access: The strong consistency model in S3 eliminates the need for complex application logic to handle eventual consistency. Your applications can rely on the fact that any successful write will be immediately visible to subsequent read operations.

  3. Simplified Application Design: By providing strong read-after-write consistency, S3 simplifies the design and implementation of your applications. You don't have to implement additional mechanisms to ensure data consistency, which can reduce development time and complexity.

  4. Improved User Experience: The strong consistency in S3 ensures that your users always see the latest data, providing a seamless and reliable experience when interacting with your applications.

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