Amazon SQS FIFO Queue with Multi-Threaded Consumer - Ensuring Order Per MessageGroupId

I have a Spring Boot Java application that consumes messages from an Amazon SQS FIFO queue using the @SQSListener annotation. My consumer is multi-threaded, and I have maxConcurrentMessages set to 5, allowing multiple threads to process messages simultaneously.

I understand that SQS FIFO queues maintain the order of messages within the same MessageGroupId and deliver them in the correct sequence. However, I’m concerned that the multi-threaded nature of my consumer might break the FIFO processing guarantees, even though the messages are received in order.

For example, if I have 5 messages (message1 to message5) from the same group (groupA) in the queue, they are delivered in order and can all be in-flight at the same time in the consumer. Since my consumer uses multiple threads, these messages could be split across 5 different threads. My worry is that this setup could cause the messages to be processed out of order, breaking the FIFO guarantee of the queue.

My Questions Are:

1. Can the multi-threaded consumer potentially break FIFO processing within the same MessageGroupId, even if messages are delivered in order and are in-flight simultaneously?
2. What is the best way to ensure that messages within the same group are processed in the correct order, even with a multi-threaded consumer setup?
3. Are there any best practices, synchronization techniques, or specific configurations that can help maintain strict ordering of messages in a multi-threaded environment?

I appreciate any insights or advice on how to manage this scenario effectively!