How to Process Multi-Region EFS Data in One Region with Least Effort?
A company has AWS resources in multiple AWS Regions. The company has an Amazon EFS file system in each Region where the company operates. The company’s data science team operates within only a single Region. The data that the data science team works with must remain within the team's Region. A data engineer needs to create a single dataset by processing files that are in each of the company's Regional EFS file systems. The data engineer wants to use an AWS Step Functions state machine to orchestrate AWS Lambda functions to process the data. Which solution will meet these requirements with the LEAST effort?
Community Insight
The exam tests selecting a managed cross-Region data movement approach that keeps processing inside the team's Region; the trap is choosing DataSync because it consolidates files, even though EFS replication requires less operational effort.
Amazon EFS replication can copy each Regional file system into the data science team's Region so Lambda functions mount local replicas and process the data while meeting residency with minimal operational effort. This page establishes why EFS replication is the least-effort answer over DataSync, cross-Region mounts, or multi-Region Lambda deployments.
Many learners pick D and use AWS DataSync to consolidate every Regional EFS file system into the team's Region; that can work, but it adds migration-style tasks and destination management, so it is not the least-effort solution.
Community Discussion (7 comments)
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Expert Analysis
Why the Answer Is Correct
Option B is the least-effort compliant design because EFS replication is a native, managed feature that creates a replica of each Regional file system in the data science team's Region. Once replication is configured, the Step Functions state machine can invoke Lambda functions in the team's Region to mount the local replica file systems and process the files, so the data the team works with is resident in that Region. The replication setup is simpler than building DataSync tasks or deploying and coordinating Lambda functions in every source Region. This matches the requirement to create one processed dataset from all Regional EFS sources without moving the processing workload outside the team's Region.Why the Other Options Are Wrong
Option A tries to peer VPCs and mount each Regional EFS file system directly from the team's Region; EFS is a Regional service and does not support cross-Region mounts, and EFS file locking does not solve that. Option C deploys Lambda and processing into each source Region, which puts the team's data-processing workload outside its required Region and adds multi-Region deployment and orchestration effort. Option D can copy files into the team's Region with DataSync, but DataSync is a migration/transfer tool that requires per-source tasks and destination file-system management, so it is not the least-effort path compared with native EFS replication.Community Comment Notes
RenatoFonseca points to the EFS replication documentation and argues that replication automatically synchronizes data to the team's Region with minimal setup, which aligns with option B. Arnaud92 reads the residency rule strictly and concludes only C remains valid, but that interpretation allows the team's processing to run in each source Region, conflicting with the single-Region requirement. pedrobpc objects that option D "Moves raw data across Regions" and raises a residency concern, while Vidhi212 favors DataSync for consolidation; the stronger exam reading is that EFS replication is the lower-effort managed way to bring data into the team's Region for local Lambda processing. HagarTheHorrible's note that DataSync is for large-scale migration further supports treating D as heavier than needed.Official Reference
Exam Strategy
When a question says 'LEAST effort' and names a native replication feature for the exact source and destination, prefer that managed feature over general-purpose transfer tools. Check whether the processing tier must stay in the required Region, because deploying Lambda in each source Region is more work and may break residency.
Frequently Asked Questions
Why is AWS DataSync not the least-effort choice for this multi-Region EFS scenario?
DataSync can copy files into the team's Region, but it requires per-source transfer tasks and destination EFS management. EFS replication is the native managed feature for this pattern.
Can a Lambda function in one Region mount an EFS file system from another Region?
No. EFS mount targets are Regional, so cross-Region mounts are not supported; this is why option A's VPC peering approach fails.
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