Batch Apex is a powerful Salesforce feature that helps process large volumes of data asynchronously, making it an essential skill for Salesforce Developers. This blog provides answers to 36 commonly asked Batch Apex interview questions, helping you prepare for your next interview with confidence.
List of Questions
Here’s the complete list of all 36 questions covered in this guide:
- What is Batch Apex in Salesforce?
- What are the three main methods in a Batch Apex class?
- Why use Batch Apex when tools like Data Loader exist?
- What is the default and maximum size of a batch?
- What is the maximum number of batches that can be executed concurrently?
- What is the maximum number of records a Batch Apex job can process?
- What is the maximum number of concurrent executions of the start method?
- What is the maximum number of jobs in the Holding status in the Apex flex queue?
- Can you run a Batch Apex job in a trigger?
- What interface implements Batch Apex in Salesforce?
- Can a Batch Apex job be paused or resumed?
- Is the order of execution for batches guaranteed?
- What is the purpose of the
finishmethod in Batch Apex? - How can you schedule a Batch Apex job to run at a future time?
- What is the advantage of using
Database.QueryLocatorin Batch Apex? - Can we call one batch class from another batch class?
- What happens if a batch encounters errors? Will the entire batch job roll back?
- How can you ensure only problematic records are rolled back?
- Can future methods be called from a batch class?
- How do you make callouts from a batch class?
- How do you track the status of a batch class?
- Can batch classes be reordered in the Apex flex queue?
- How can you track total success and failed records and send a summary email?
- How can you abort a Batch Apex job?
- What happens if an unhandled exception occurs in the
executemethod? - How do you publish platform events in Batch Apex?
- What is the difference between
Database.QueryLocatorandIterable? - How do you optimize Batch Apex to avoid hitting governor limits?
- Write a Batch Apex class to update
OpportunityStagebased onCloseDate. - What are the different possible statuses for a Batch Apex job?
- What are the limitations of Batch Apex?
- How would you implement infinite scrolling for large datasets in Batch Apex?
- What considerations are necessary for handling large datasets with SOQL in Batch Apex?
- How do you handle errors when multiple batches are running simultaneously?
- Can Batch Apex fire platform events? How?
- How can Batch Apex dynamically manage changing business needs?
Detailed Questions and Answers
1. What is Batch Apex in Salesforce?
Answer: Batch Apex is used to process large volumes of data asynchronously. It breaks records into smaller manageable chunks, bypassing governor limits for large-scale operations.
2. What are the three main methods in a Batch Apex class?
Answer:
start: Retrieves records to process.execute: Processes each batch of records.finish: Handles post-processing logic.
3. Why use Batch Apex when tools like Data Loader exist?
Answer: Batch Apex is ideal for complex logic, runtime calculations, or dynamic queries, which cannot be achieved with static tools like Data Loader.
4. What is the default and maximum size of a batch?
Answer: The default size is 200 records, and the maximum size is 2,000 records.
5. What is the maximum number of batches that can be executed concurrently?
Answer: A maximum of 5 batch jobs can be active or queued simultaneously.
6. What is the maximum number of records a Batch Apex job can process?
Answer: Batch Apex can process up to 50 million records.
7. What is the maximum number of concurrent executions of the start method?
Answer: Only 1 concurrent execution is allowed.
8. What is the maximum number of jobs in the Holding status in the Apex flex queue?
Answer: A maximum of 100 jobs can be in the Holding status.
9. Can you run a Batch Apex job in a trigger?
Answer: Yes, but it’s not recommended due to potential performance issues.
10. What interface implements Batch Apex in Salesforce?
Answer: Database.Batchable interface.
11. Can a Batch Apex job be paused or resumed?
Answer: No, but chaining Batch Apex jobs can achieve similar functionality.
12. Is the order of execution for batches guaranteed?
Answer: No, factors like system resources can affect execution order.
13. What is the purpose of the finish method in Batch Apex?
Answer: It handles post-processing tasks like sending emails or logging results.
14. How can you schedule a Batch Apex job to run at a future time?
Answer: Use System.scheduleBatch with a delay.
15. What is the advantage of using Database.QueryLocator in Batch Apex?
Answer: It bypasses the SOQL record limit and can process up to 50 million records.
16. Can we call one batch class from another batch class?
Answer: Yes, but only from the finish method.
17. What happens if a batch encounters errors?
Answer: Only the failed batch is rolled back; previous successful batches remain committed.
18. How can you ensure only problematic records are rolled back?
Answer: Use Database.SaveResult to handle errors record by record.
19. Can future methods be called from a batch class?
Answer: No, as both are asynchronous operations.
20. How do you make callouts from a batch class?
Answer: Implement Database.AllowsCallouts in the batch class.
21. How do you track the status of a batch class?
Answer: Use the job ID or Apex flex queue to monitor progress.
22. Can batch classes be reordered in the Apex flex queue?
Answer: Yes, via the UI or System.FlexQueue methods.
23. How can you track total success and failed records?
Answer: Use Database.Stateful to maintain state and send an email in the finish method.
24. How can you abort a Batch Apex job?
Answer: Use System.abortJob(jobId).
25. What happens if an unhandled exception occurs in the execute method?
Answer: The job terminates unless error handling is implemented.
26. How do you publish platform events in Batch Apex?
Answer: Implement Database.RaisesPlatformEvents in the batch class.
27. What is the difference between Database.QueryLocator and Iterable?
Answer: QueryLocator supports up to 50 million records; Iterable is limited by governor limits but allows custom logic.
28. How do you optimize Batch Apex?
Answer: Use smaller batches, avoid DML in loops, and write efficient queries.
29. Write a Batch Apex class to update OpportunityStage.
Answer: Use a query in start, update records in execute, and log results in finish.
30. What are the possible statuses for a Batch Apex job?
Answer: Holding, Queued, Preparing, Processing, Completed, Failed, Aborted.
31. What are the limitations of Batch Apex?
Answer: Limited to 5 active jobs, 100 in Holding status, and 50 million records.
32. How would you implement infinite scrolling?
Answer: Use Database.QueryLocator with offset pagination.
33. How do you handle errors in multiple batches?
Answer: Use Database.SaveResult and Database.Stateful.
34. Can Batch Apex fire platform events?
Answer: Yes, by implementing Database.RaisesPlatformEvents.
35. How can Batch Apex dynamically manage business needs?
Answer: Use custom metadata or settings to control behavior.
Conclusion
These 36 questions cover everything you need to know about Batch Apex. Use this guide to prepare for interviews, optimize your knowledge, and confidently tackle real-world challenges in Salesforce development.
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