In terms of the processing of an e-transfer transaction, you're correct. A number of transactions taking place are transmitted nearly in real time.
In terms of the speed, those decisions and transactions are often implemented and influenced by the financial institution involved. Based on risk factors and fraud checks in the system, there are a number of factors that go into this. Ultimately, the purpose is to ensure that any suspicious transactions are flagged and that there can be a process to ensure fraud is mitigated on the network.