A solutions architect is designing a two-tier application to collect and process registration forms. The application must process submitted forms quickly, ensure each form is processed exactly once, and guarantee no data loss. Which solution meets these requirements?

An Amazon SQS FIFO (First-In, First-Out) queue is the correct choice because it guarantees both message ordering and exactly-once processing, which are critical requirements for processing registration forms without data loss or duplication. The "exactly once" processing is achieved through message deduplication. An Amazon API Gateway HTTP API is incorrect because it's a synchronous request/response service, not a queuing service designed for asynchronous processing, ordering, or exactly-once delivery. An Amazon SQS standard queue is incorrect because it does not guarantee message ordering or exactly-once processing. While it offers at-least-once delivery, it can deliver messages multiple times and out of order. An AWS Step Functions synchronous workflow is incorrect because it is designed for coordinating distributed applications and microservices, not primarily for asynchronous queuing with exactly-once processing guarantees for individual messages. A synchronous workflow would also block the web application until the worker completes, which is not ideal for quick form submission.