In which part of a financial product can synchronous calls be made, and where is asynchrony needed?

Synchronous calls in a financial product are appropriate where an immediate response and confirmation of the operation are required, for example:

• Balance check during payment
• Payment authorization
• Obtaining the current exchange rate

Asynchronous operations are needed where tasks may take a long time or do not require immediate results:

• Processing large volumes of transactions
• Generating reports
• Sending notifications
• Integration with external systems where delays are possible

Using asynchronous methods helps avoid blocking the user interface and increases system scalability.