Very good question. I will provide a diagram that can illustrate this infrastructure. Great feedback.

Even though banks (or organization) have their unique infrastructure, the core of what they have consists of what I described in this article. This infra is the something you can build upon to make it as complex as you want depending on your specific requirements.

While you can use this infra for a bank, you can also use it for any product/service you provide.

I hope this makes sense.