Amazon’s AWS has a message queue system, aka SQS, to which they have recently started adding a variant which assures that your messages are delivered in the same order that they got sent.  I.e. first in first out.

If you are surprised that they don’t do that by default you may enjoy thinking about what would be involved if the Post Office was to decide to offer this feature.

That said, I’ve been surprised that it took so long for this to show up and I remain surprised how slowly they are rolling it out.

So it is with some amusement I read in their doc an example of why you might want this feature.

“Display the correct product price by sending price modifications in the right order.”

Which I think helps explain why Seattle is one of the few AWS sites that supports it so far.