Preparing for a Salesforce interview requires a deep understanding of various concepts, especially when it comes to Asynchronous Apex, a powerful feature for handling long-running operations efficiently. In this blog, we’ve compiled the Top Salesforce Interview Questions on Asynchronous Apex, covering everything from future methods to batch processing, and best practices for handling large data operations. Whether you’re a beginner or a seasoned professional, these questions and answers will help you master Asynchronous Apex and confidently tackle interview challenges.

Q1. Can you explain Asynchronous Apex?

Asynchronous Apex allows time-consuming tasks to execute in a separate thread, preventing performance bottlenecks in the main execution. This is especially useful for processing large volumes of data or long-running jobs, as it avoids governor limits like heap size and timeout errors. These jobs run in the background and are processed when system resources are available.

Q2. What are the different types of Asynchronous Apex in Salesforce?

1. Future Methods: Used for executing tasks at a later time.
2. Batch Apex: Handles large-scale data operations in manageable chunks.
3. Queueable Apex: Enables chaining and tracking of jobs.
4. Scheduled Apex: Schedules jobs to execute at specific intervals.
5. Platform Events: Facilitates real-time event-driven communication.

Q3. Why is Asynchronous Apex preferred for time-consuming tasks?

Running long tasks synchronously can result in governor limit violations such as heap size and execution time errors. Asynchronous Apex mitigates these issues by executing these operations in the background without affecting the main transaction.

Q4. Can triggers directly invoke web service callouts?

No, triggers cannot make synchronous web service callouts as it would block the database transaction. To perform web service callouts, you should use asynchronous methods like @future.

Q5. Is it possible for a future method to invoke another future method?

No, chaining future methods is not allowed in Salesforce.

Q6. What are the advantages of using Batch Apex?

• Each batch has a fresh set of governor limits.
• Automatic division of records into smaller, manageable batches.
• Fault tolerance: If one batch fails, other batches still proceed without rollback.

Q7. Why should you choose Batch Apex over regular Apex?

• Query Limit: Batch Apex can retrieve up to 50 million records, compared to 50,000 in regular Apex.
• Processing Limit: Batch Apex processes 200 records per execution, double the limit of synchronous Apex.
• Heap Size: Batch Apex has a 12 MB heap size, compared to 6 MB in regular Apex.
• Error Management: Batch Apex handles errors more effectively without affecting successfully processed records.

Q8. What are best practices for implementing Batch Apex?

• Use regular Apex for small data operations.
• Avoid creating multiple batch jobs within a trigger.
• Do not call future methods from Batch Apex.
• Optimize SOQL queries in the Batch Apex class.
• Use the Database.insert method with allOrNone = false to handle partial failures.

Q9. How many jobs can you schedule using Scheduled Apex?

A maximum of 100 Apex jobs can be scheduled concurrently in an organization.

Q10. Are synchronous callouts supported in Scheduled Apex?

No, synchronous callouts are not supported. However, a scheduled job can invoke a Batch Apex process, which can then perform a web service callout.

Q11. What are the best practices for writing future methods?

• Minimize the number of asynchronous requests to avoid queue delays.
• Group multiple callouts into a single future method when possible.
• Use future methods sparingly for large datasets; Batch Apex is more efficient.

Q12. Why can’t sObject parameters be passed to future methods?

The state of an sObject may change before the future method executes, causing inconsistencies. Hence, sObjects cannot be passed directly.

Q13. Can a Queueable job that doesn’t allow callouts chain another that does?

Yes, you can chain jobs with differing callout requirements.

Q14. Is it possible to invoke Queueable Apex within a Batch Apex class?

Yes, but only one Queueable job can be enqueued per execution of the execute method to prevent overloading the system.

Q15. Can future methods be called from a Batch Apex class?

Future methods cannot be invoked directly from the execute method of a Batch Apex class. However, a workaround involves calling a web service that internally invokes a future method.

Q16. How can future methods help avoid Mixed DML errors?

Mixed DML errors occur when performing DML on setup and non-setup objects in the same transaction. Future methods isolate these operations by running the setup or non-setup DML in a separate transaction.

Q17. What happens when a Batch Apex job encounters an error during processing?

If a batch fails while processing, the rest of the batches continue to execute. For example, with a batch size of 200, if the 298th record fails, records 201-400 will either:

• Rollback entirely (if normal DML is used).
• Partially commit (if Database.insert with allOrNone = false is used).

Q18. What is the difference between Database.QueryLocator and Iterable<sObject>?

• Database.QueryLocator: Returns up to 50 million records and uses a SOQL query to define the scope.
• Iterable<sObject>: Allows custom logic to define record scope but is subject to the standard SOQL limit of 50,000 records.

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