Some message brokers are highly optimized for "at most once" delivery, where you want to receive the message between 0 and 1 times but you NEVER want to receive

Some message brokers are highly optimized for "at most once" delivery, where you want to receive the message between 0 and 1 times but you NEVER want to receive the message twice. Others are optimized for "at least once" delivery where you MUST receive the message at least once, but you don't mind if you receive it more than once. Additionally, different message brokers have varying levels of support for clustering, and varying responses to failure scenarios like network partions.