The scenario that necessitates that the callout be made in an asynchronous method is when the callouts will be made in an Apex trigger. An Apex trigger is a piece of Apex code that executes before or after specific data manipulation language (DML) events occur, such as inserting, updating, or deleting records. A callout is a request that is sent from Apex code to an external web service. Apex does not allow callouts to be made from triggers, as triggers are synchronous and run in the same transaction as the DML operation. Callouts are asynchronous and may take a long time to complete, which can cause the transaction to exceed the governor limits or lock the database resources. Therefore, the developer must use an asynchronous method, such as a future method, a queueable class, or a batch class, to make the callout from the trigger. An asynchronous method runs in a separate thread and does not block the execution of the trigger or the DML operation. Reference: [Apex Triggers], [Apex Web Services and Callouts], [Asynchronous Apex]