Amazon Web Services SAA-C03 Online Access

The optimal way to improve reliability and scalability of SFTP on AWS is to use AWS Transfer Family (for SFTP). It provides a fully managed SFTP server integrated with Amazon S3.

No EC2 instances or infrastructure management is required.

AWS Transfer Family supports custom DNS domains (e.g., sftp.example.com) and allows integration with existing authentication mechanisms like LDAP, AD, or custom identity providers.

Files are uploaded directly to S3, eliminating the need for cron jobs to move data from EC2 to S3.

Built-in high availability and scalability removes the burden of managing infrastructure.

Other options:

A and D still require manual scaling, server maintenance, and cron jobs.

C (Storage Gateway) is used for hybrid file access, not for replacing an SFTP server.

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AWS Transfer Family for SFTP

The best answer isAPI Gateway + SQS + DLQ + Lambdabecause it combines API ingestion with durable queuing and asynchronous processing. AWS guidance for event-driven serverless architectures specifically recommends usingAmazon SQSto decouple components and durably persist messages when downstream processing is slower or bursty. AWS also documents thatdead-letter queueshelp isolate messages that fail processing, which supports the requirement to avoid losing requests. API Gateway can integrate with AWS services, including SQS, to accept requests from mobile and web clients. The ALB options do not provide the same durable buffering, and the SNS option is less appropriate because the key requirement is loose coupling with durable request preservation. Therefore,Bis the strongest design. (AWS Documentation)

Provisioned IOPS SSD (io1 or io2) is designed for I/O-intensive workloads that require low latency and consistent throughput, which is critical for transactional and production databases. It provides predictable performance, unlike General Purpose SSD, which is burst-based.

Amazon SQS FIFO is the correct answer because the question explicitly requires that every order be processed exactly once and that order state be preserved even during outages or pauses. AWS documentation states that FIFO queues support exactly-once processing and maintain message order. Using a queue also decouples the frontend from the backend so orders are durably stored until workers can process them. That directly protects against lost or incomplete order processing during spikes or temporary failures. The other options improve availability in other ways but do not provide durable exactly-once message handling for the order workflow. Therefore, placing the backend behind an SQS FIFO queue is the strongest design.

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