Intoduction
Asynchronous Apex is a cornerstone of Salesforce development, enabling developers to run processes in the background, handle large datasets, and perform complex operations without impacting user experience.
Whether you’re making callouts to external systems, processing millions of records, or scheduling tasks to run at specific times, Asynchronous Apex provides the tools to get the job done efficiently.
In this first part of our series, we’ll explore 25 fundamental interview questions on Asynchronous Apex, covering Future Methods, Batch Apex, Queueable Apex, and Scheduled Apex.
These questions are designed to help you understand the basics, limitations, and use cases of asynchronous processing in Salesforce.
Whether you’re preparing for an interview or looking to strengthen your Salesforce skills, this post will set the stage for mastering Asynchronous Apex. Let’s get started!
1. What is the difference between Synchronous Apex and Asynchronous Apex?
| Synchronous Apex | Asynchronous Apex |
|---|---|
|
Immediate Execution:
Blocking Operation: Since it runs in real time, users must wait for the operation to finish before interacting further with the system. Use Cases: Trigger is an example of synchronous apex that runs right after the record is saved, updating records in real-time. Types: Synchronous apex includes – Apex Triggers, Record Trigger Flow |
Background Execution: Asynchronous Apex runs in the background, allowing the system to move on to other tasks while the process continues to execute. Non Blocking Operation: In case of asynchronous operation, users do not have to wait for the operation to finish, they can continue working while the background task is processed. Use Cases: Ideal for long running processes, such as data operations, callout to external services and scheduled tasks. Types: Asynchronous apex includes – Batch Apex, Future Methods, Queueable Apex and Scheduled Apex. |
2. What are the different types of Asynchronous Apex?
The types of Asynchronous Apex are:
Future Methods
Batch Apex
Queueable Apex
Scheduled Apex
Explanation:
Each type serves a different purpose:
Future Methods:Â Run small tasks in the background.
Batch Apex:Â Process large datasets in chunks.
Queueable Apex:Â Chain jobs and perform complex tasks.
Scheduled Apex: Used to schedule and run jobs at specific times.
3. What is a Future Method in Salesforce?
Answer:
A Future Method is an asynchronous method that runs in the background. It is annotated with @future.
Explanation:
Future methods are used for tasks like making callouts to external systems or performing operations that don’t need to block the user interface.
4. Can Future Methods return values?
Answer:
No, Future Methods cannot return values because they run asynchronously.
Explanation:
Since Future Methods run in the background, there’s no way to return a value to the calling code immediately.
5. What are the limitations of Future Methods?
Answer:
Limitations include:
Cannot return values.
Cannot call another Future Method.
Cannot be used in triggers withÂ
after events.Limited to 50 Future calls per Apex transaction.
Explanation:
These limitations ensure that Future Methods are used for simple, non-dependent tasks.
6. What is Batch Apex in Salesforce?
Answer:
Batch Apex is used to process large amounts of data in smaller chunks (batches). It implements the Database.Batchable interface.
Explanation:
Batch Apex is ideal for tasks like updating millions of records or performing complex calculations on large datasets.
7. What are the three methods in Batch Apex?
Answer:
The three methods are:
Start:Â Prepares the data for processing.
Execute:Â Processes each batch of records.
Finish:Â Performs post-processing tasks.
Explanation:
Start:Â Identifies the records to process.
Execute:Â Processes each batch.
Finish:Â Runs after all batches are processed.
8. What is the scope of a Batch Apex job?
Answer:
The scope is the number of records processed in each batch. The default is 200 records.
Maximum is 2000 records and Minimum is 1 record.
Explanation:
You can adjust the scope to balance performance and resource usage.
9. What is Queueable Apex?
Answer:
Queueable Apex is an enhanced version of Future Methods that allows chaining of jobs and more complex operations.
Explanation:
Queueable Apex is used when you need to perform multiple asynchronous tasks in a specific order.
10. Can Queueable Apex call another Queueable job?
Answer:
Yes, Queueable Apex can chain jobs by calling another Queueable job.
Explanation:
This allows you to create a sequence of asynchronous tasks.
11. What is Scheduled Apex?
Answer:
Scheduled Apex allows you to run Apex classes at specific times using the Salesforce scheduler.
Explanation:
It is used for tasks like daily data cleanup or nightly reports.
12. How do you schedule an Apex class?
Answer:
You can schedule an Apex class using the System.schedule method or the Salesforce UI.
Explanation:
The System.schedule method takes the job name, cron expression, and an instance of the class to run.
13. What is a cron expression?
Answer:
A cron expression is a string that defines the schedule for a job. It consists of six or seven fields representing seconds, minutes, hours, etc.
Explanation:
For example, 0 0 12 * * ? means the job runs at 12 PM every day.
14. What is the difference between Future and Queueable Apex?
Answer:
Future Methods are simpler but have limitations like no chaining.
Queueable Apex supports chaining, higher limits, and more complex operations.
Explanation:
Queueable Apex is more flexible and powerful than Future Methods.
15. Can you call a Future Method from a Trigger?
Answer:
Yes, you can call a Future Method from a trigger, but only in before triggers or after triggers that don’t update the same object.
Explanation:
This avoids recursion and governor limit issues.
16. What is the maximum number of Future Method calls per transaction?
Answer:
The maximum is 50 Future Method calls per transaction.
Explanation:
This limit ensures that the system doesn’t get overloaded with too many background tasks.
17. What is the purpose of the Database.Stateful interface in Batch Apex?
Answer:
The Database.Stateful interface allows you to maintain state across batch executions.
Explanation:
Without it, variables are reset after each batch.
18. Can you call a Batch Apex job from a Trigger?
Answer:
Yes, you can call a Batch Apex job from a trigger using Database.executeBatch.
Explanation:
This is useful for processing large datasets triggered by record changes.
19. What is the maximum batch size in Batch Apex?
Answer:
The maximum batch size is 2,000 records.
Explanation:
Larger batches can cause performance issues, so Salesforce limits the size.
20. What is the difference between Batch Apex and Queueable Apex?
Answer:
Batch Apex is for processing large datasets in chunks.
Queueable Apex is for chaining jobs and performing complex tasks.
Explanation:
Batch Apex is data-focused, while Queueable Apex is task-focused.
21. Can you call a Future Method from a Batch Apex job?
Answer:
No, you cannot call a Future Method from a Batch Apex job.
Explanation:
Future Methods are designed for simpler tasks and cannot be used within Batch Apex
22. What is the purpose of the Finish method in Batch Apex?
Answer:
The Finish method is used for post-processing tasks, such as sending emails or logging results.
Explanation:
It runs after all batches are processed.
23. Can you schedule a Batch Apex job?
Answer:
Yes, you can schedule a Batch Apex job using Scheduled Apex.
Explanation:
This allows you to run batch jobs at specific times.
24. What is the maximum number of Batch Apex jobs that can be queued at once?
Answer:
The maximum is 5 queued or active Batch Apex jobs.
Explanation:
This limit prevents overloading the system.
25. What is the difference between Database.executeBatch and System.enqueueJob?
Answer:
Database.executeBatch is used to start a Batch Apex job.System.enqueueJob is used to start a Queueable Apex job.
Explanation:
They are used for different types of asynchronous processing.
Conclusion
Asynchronous Apex is a powerful feature in Salesforce that enables developers to handle long-running tasks, process large datasets, and perform complex operations without blocking the user interface or other processes.
In this first part of our series, we covered 25 essential interview questions on Asynchronous Apex, focusing on Future Methods, Batch Apex, Queueable Apex, and Scheduled Apex. These questions provide a solid foundation for understanding the basics of asynchronous processing in Salesforce, including its use cases, limitations, and best practices.
Whether you’re preparing for a Salesforce developer interview or looking to deepen your knowledge of Asynchronous Apex, these questions and answers will help you grasp the core concepts and prepare you for more advanced topics. Stay tuned for Part 2, where we’ll dive deeper into Batch Apex, Queueable Apex, and their interactions with other Salesforce features.
