Hi there,
I don't think so, looking at the Campaign API document, it provides how to use the product, it does not provide general design considerations that are not Adobe specifics in a sense that integration via APIs design should always follow industry best practices. and as such, if you want to build a strong and robust solution API based, you need to take into account that the 3rd party system you are calling might have issues (like the caller system can have some too), and error handling and retry / queueing is some of these best practices that should be taken into considerations.
Also, for ACS Transactional Message APIs, you must be aware of the product limitations that are contractual, (See https://helpx.adobe.com/legal/product-descriptions/campaign-standard.html and search for Dedicated Server, 50,000 / hour), therefore, you also need to take that also into account from a volume pespective. If your volume of transactional messages will exceed the 50,000 / hour at peak time, you have to increase the capacity of ACS. Some customers have used queueing to throttle the transaciotnal messages into ACS to fit within the 50,000 / h range....
Hope this helps.
Thanks
Denis