Which of the following is the best approach for asynchronous processing in Salesforce?

The best approach for asynchronous processing in Salesforce is indeed the combination of an After-Save Flow Trigger and Apex. This method takes advantage of the strengths of both declarative tools and programmatic capabilities, ensuring a robust solution for handling complex business logic or large data volumes.

Using an After-Save Flow Trigger allows for the automation of business processes immediately after changes are made to records, which can efficiently handle certain tasks without needing to write code. However, in situations that require more intricate processing, Salesforce’s Apex programming capabilities can step in, providing increased flexibility and control. The advantage of integrating Apex with the Flow Trigger is that it allows for more complex operations, such as bulk processing and error handling, which can be crucial for large datasets or specific business requirements.

This combination also allows for a clear separation of concerns, where flows can handle standard automation scenarios while Apex can deal with custom logic or operations that go beyond the capabilities of Flow alone. This makes it an ideal choice for asynchronous processing, as it balances performance with the ability to manage complex logic effectively.

The other options, while they have their merits, do not offer the same level of flexibility or capability for complex asynchronous processing.