Basic Batch Apex Interview Questions
Basic Batch Apex Interview Questions
Introduction
Batch Apex is a powerful asynchronous processing feature in Salesforce that allows for the execution of large-scale operations on records efficiently. Below are some of the most commonly asked interview questions related to Batch Apex to help you prepare for your next interview.
1. What is Batch Apex in Salesforce?
Answer: Batch Apex is an asynchronous processing mechanism in Salesforce that enables the execution of large-volume data operations in manageable chunks. It helps bypass governor limits that apply to synchronous Apex code.
2. What are the three main methods in a Batch Apex class?
Answer: A Batch Apex class implements the Database.Batchable interface and consists of three main methods:
- start(Database.BatchableContext BC): Defines the batch scope by querying records.
- execute(Database.BatchableContext BC, List scope): Processes each batch of records.
- finish(Database.BatchableContext BC): Performs post-processing tasks like sending notifications.
3. What happens if a Batch Apex job fails in the middle of execution?
Answer: If a Batch Apex job fails during execution, only the failed batch is rolled back. The successfully executed batches remain committed to the database.
4. Why use Batch Apex instead of Data Loader?
Answer: While Data Loader is a manual tool for importing/exporting records, Batch Apex provides:
- Automation within Salesforce.
- Controlled execution with better error handling.
- The ability to execute logic beyond simple data operations.
5. Can you call one Batch Apex job from another?
Answer: Directly, no. However, you can chain Batch Apex jobs by calling another batch job in the finish() method.
public void finish(Database.BatchableContext BC) {
MySecondBatch job = new MySecondBatch();
Database.executeBatch(job, 200);
}
6. What is the default and max batch size?
Answer:
- Default batch size: 200 records.
- Maximum batch size: 2,000 records per batch.
7. How many batches can run concurrently?
Answer: Salesforce allows 5 concurrent Batch Apex jobs to run at a time.
8. What is Database.BatchableContext, and how is it used?
Answer:
- Database.BatchableContext provides contextual information about the Batch Apex execution.
- It is passed as an argument to start(), execute(), and finish() methods to track job progress.
9. Can you use Custom Metadata or Custom Settings in a Batch job?
Answer: Yes, Custom Metadata and Custom Settings can be referenced in a Batch Apex job to store configuration data.
10. What is the maximum number of records a Batch Apex job can process?
Answer: A single Batch Apex job can process up to 50 million records.
11. What happens if a Batch Apex job exceeds heap size limits?
Answer: The batch execution will fail, and Salesforce will generate a System.LimitException: Heap size too large error.
12. How many concurrent executions of start() are allowed?
Answer: Up to 5 concurrent executions of the start() method are allowed at any given time.
13. How many jobs can be in Holding status in the Apex Flex Queue?
Answer: Up to 100 batch jobs can be in the Holding state in the Apex Flex Queue.
14. Can you run Batch Apex inside a trigger?
Answer: No, you cannot directly run a Batch Apex job inside a trigger. However, you can use future methods or queueable Apex to call a Batch Apex job indirectly.
Conclusion
Understanding Batch Apex is crucial for handling large data volumes efficiently in Salesforce. These questions and answers will help you ace your next interview by covering key Batch Apex concepts. Good luck! 🚀
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