messageGroupId

This parameter applies only to FIFO (first-in-first-out) topics. The MessageGroupId can contain up to 128 alphanumeric characters (a-z, A-Z, 0-9) and punctuation (!"#$%&'()*+,-./:;<=>?@[\]^_{|}~)`.

The MessageGroupId is a tag that specifies that a message belongs to a specific message group. Messages that belong to the same message group are processed in a FIFO manner (however, messages in different message groups might be processed out of order). Every message must include a MessageGroupId.