The domain is obviously very complex as its not just a ledger, but risk, loans, overdrafts, savings, etc as well as premium offerings, interacting with different payments networks like FasterPayments and Mastercard. Then there are the budgeting features, payments between friends, support system (Which is probably quite complex in its self), card issuing, internal dashboards and metric services, etc, etc, etc. I can easily see how this gets to 2000 services and I didn't even begin to think about the business accounts, US accounts, etc.