The AWS documentation makes it sound like SQSEvent.Records will only ever return a single record at a time if using FIFO with MessageGroupId. Is this truly what happens? If so, I am really going to have to do some work, because I was hoping to batch process the ordered records to speed things up.

Messages within the same message group are processed in order, and only one message from each group is processed at a time to maintain this order.

https://docs.aws.amazon.com/AWSSimpleQueueService/latest/SQSDeveloperGuide/fifo-queue-lambda-behavior.html#fifo-queue-message-grouping