The Cucumber Book, 2nd Edition

Our New Asynchronous Architecture

In a real banking system, the ATM isn’t the only thing making debits on your account. You might use your debit card in a restaurant or supermarket, or you might walk into a bank and withdraw cash over the counter. You might have written a check that gets cashed a few days later. You’ll also get credits into your account, like when you deposit checks at the bank. The bank treats each of these events as a transaction, which it processes some time after the actual event has happened. Note that this kind of transaction is completely different from a database transaction, which we’ll talk about in the next chapter.

We’re going to change our architecture so that when the customer makes a withdrawal from the ATM, ...