A Lambda function consumes messages from an Amazon SQS standard queue but sometimes processes the same message multiple times. What is the most cost-effective way to stop duplicate processing?

Replacing the SQS standard queue with an SQS FIFO (First-In, First-Out) queue and utilizing its message deduplication feature is the most cost-effective and direct solution. SQS FIFO queues guarantee exactly-once processing and prevent duplicate messages from being delivered for a specified deduplication interval, which directly addresses the problem of duplicate processing. Configuring a dead-letter queue (DLQ) helps manage messages that fail processing but does not prevent duplicate processing of successfully delivered messages. Setting the Lambda function's reserved concurrency to 1 would severely limit throughput and introduce a bottleneck, not solve the root cause of SQS delivering duplicates in a standard queue. Switching to Amazon Kinesis Data Streams is a more complex and expensive solution designed for real-time data streaming, which is overkill for simply preventing duplicate message processing from a queue.