How to automatically replicate new S3 objects to us-west-2 with least overhead?
A company stores critical files in an Amazon S3 bucket in the us-east-1 AWS Region. To comply with disaster recovery requirements, all new objects in the bucket must automatically replicate to a bucket in the us-west-2 Region. Which solution will meet this requirement with the LEAST operational overhead?
Community Insight
You are being tested on picking a managed S3 feature over self-built automation for cross-Region durability; the trap is assuming a lifecycle rule or Lambda function can substitute for CRR.
This question tests whether you can choose the native, lowest-overhead mechanism for copying every new object from a us-east-1 S3 bucket to a us-west-2 bucket. The page confirms that S3 Cross-Region Replication with versioning is the correct answer, since AWS performs the copy automatically without any custom code.
The most common wrong pick is the Lambda plus EventBridge option (C), because it appears to work logically, but it adds custom code, retry logic, and monitoring overhead that the question explicitly asks you to minimize.
Community Discussion (1 comments)
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Expert Analysis
Why the Answer Is Correct
Option A uses S3 Cross-Region Replication (CRR), the managed feature purpose-built for copying objects between buckets in different Regions. Once a replication rule names the us-west-2 destination bucket and versioning is enabled on the source bucket, every new object is replicated asynchronously by S3 itself with no servers, code, or schedules to maintain. This satisfies the disaster recovery requirement while keeping operational overhead at the minimum, which is exactly what the question asks for. As Bad_Mat noted, the winning statement is to "Enable Cross-Region Replication (CRR) on the source bucket" and point it at the destination bucket. Practically, versioning must also be enabled on the destination bucket or the replication configuration will not save, but that does not weaken A as the answer.Why the Other Options Are Wrong
Option B misunderstands CORS entirely: Cross-Origin Resource Sharing only controls which web origins may read bucket content from a browser, and it never copies objects between buckets or Regions. Option C would technically move data, but it forces you to own the Lambda code, the EventBridge rule, retry and error handling, IAM permissions, throttling, and payload/time limits for large objects, which is far more operational overhead than a native replication rule. Option D confuses storage-class transitions with replication; S3 Lifecycle policies operate inside a single bucket and can only transition or expire objects, they cannot place copies in a bucket in another Region.Community Comment Notes
The only learner comment on this question, from Bad_Mat, endorses option A and quotes the core of the solution: "Enable Cross-Region Replication (CRR) on the source bucket." That aligns with the vendor's documented behavior that CRR replicates new objects automatically once configured. No commenter argues for CORS, Lambda, or lifecycle transitions, so there is no dissent to reconcile with the vendor documentation.Official Reference
Exam Strategy
When a scenario says "least operational overhead," eliminate any answer that requires you to write or maintain code, then look for a managed service feature. For S3 cross-Region copying, remember that versioning is a prerequisite on both source and destination, and that lifecycle rules never cross Region boundaries.
Frequently Asked Questions
Does S3 Cross-Region Replication require versioning on both buckets?
Yes. Versioning must be enabled on the source bucket and on the destination bucket, otherwise S3 will not save the replication configuration.
Why is a Lambda plus EventBridge copy function not the best answer here?
It works but adds custom code, retries, IAM setup, and monitoring to maintain, which is exactly the operational overhead the question asks you to avoid.
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