Batch Apex Scenario Based Interview Questions and Answers

global class MyBatch implements Database.Batchable<sObject>{

global Database.QueryLocator start(Database.BatchableContext BC) {
return Database.getQueryLocator([SELECT Id, Name FROM Account]);
}

global void execute(Database.BatchableContext BC, List<Account> scope) {
List<Database.SaveResult> saveResults = Database.update(scope, false); // Update records with partial success allowed

for(Database.SaveResult sr : saveResults) {
if (!sr.isSuccess()) {
// Handle individual record errors (e.g., log the error, mark the record as failed)
for(Database.Error error : sr.getErrors()) {
// Log or take necessary action for the error
System.debug('Error occurred for record with Id: ' + sr.getId() + ', Error Message: ' + error.getMessage());
}}
}}

global void finish(Database.BatchableContext BC) {
// Perform any post-processing tasks if needed
}
}

global class MyBatchClass implements Database.Batchable<sObject>, Database.AllowsCallouts {

global Database.QueryLocator start(Database.BatchableContext bc) {
return Database.getQueryLocator('SELECT Id, Name FROM Object__c');
}

global void execute(Database.BatchableContext bc, List<sObject> scope) {
// perform execute logic
}

global void finish(Database.BatchableContext bc) {
// Optional finish method logic
}
}

Question 11. How do you track the status of the batch class?

Answer – When we execute the batch we get the job ID by which we can track the status of the batch class. There are two ways by which we can track the status

1. From UI Apex Job –  Navigate to setup –> Quick Find Box –> Search for Apex Job
2. Query on AsyncApexJob
   Example: AsyncApexJob aaj = [SELECT Id, Status, JobItemsProcessed, TotalJobItems, NumberOfErrors FROM AsyncApexJob WHERE ID =: batchprocessid ];

Question 12. Is it possible to reorder the batch class?

Answer – Batch class executes based on “first-in, first-out” in the order they have submitted. If we want to reorder the batch to make it process the first whenever the resources get available, we can do that in two ways:

1. From UI Apex Flex Queue – Batch Jobs that are in holding status go into the flex queue. To navigate to the Apex Flex queue, go to setup –> Quick Find box –> Apex Flex Queue
2. By using System.FlexQueue methods 

Syntax

Boolean isSuccess = System.FlexQueue.moveBeforeJob(jobToMoveId, jobInQueueId);

global class MyBatchClass implements Database.Batchable<sObject>,Database.Stateful {
// Define variables to store success and failure counts
global Integer successCount = 0;
global Integer failureCount = 0;

global Database.QueryLocator start(Database.BatchableContext bc) {
return Database.getQueryLocator([SELECT Id, Name FROM Object__c]);
}

global void execute(Database.BatchableContext bc, List<sObject> scope) {
// Perform callouts and process records
for (Object__c obj: scope) {
//execute logic
try {
// Increment success count

successCount++;
} catch (Exception e) {
// Handle records failure
failureCount++;
}}
}

global void finish(Database.BatchableContext bc) {
// Send email with success and failure counts
Messaging.SingleEmailMessage mail = new Messaging.SingleEmailMessage();
String[] toAddresses = new String[] {'user@example.com'};
mail.setToAddresses(toAddresses);
mail.setSubject('Batch Job Completion Report');
mail.setPlainTextBody('The batch job has completed.\n\nTotal Success Count: ' + successCount + '\nTotal Failure Count: ' + failureCount);

// Send email
Messaging.sendEmail(new Messaging.SingleEmailMessage[] { mail });
}}

Question 14. How can I abort my Batch Job?

Question 15. What happens if an unhandled exception occurs in the execute method of a Batch Apex class?

Answer – If errors are not handled properly in the Batch Job, and the execute method encounters some exceptions, then the job gets terminated. Consequently, we have to handle errors properly in the Batch Job.

For example: we can use a Database.Stateful interface to capture errors.

Question 16. How to publish platform events in the execution of batch jobs?

Answer – To fire a platform we have to implement a Database.RaisesPlatformEvents in our batch class.

Question 17. What is the difference between Database.QueryLocator and Iterable?

Answer – Major difference between Database.QueryLocator and Iterable is that with queryLocator the governor limit for the total number of records retrieved by SOQL queries is bypassed and you can query up to 50 million records. However, with an Iterable, the governor limit for the total number of records retrieved by SOQL queries is still enforced.

Also, with Iterable we can perform some custom logic and then we can pass it to execute but with queryLocator, it is simple SOQL. So If you want to perform some logic to filter your data that can’t be possible with queryLocator use Iterable. In most of the cases, it can be achieved by queryLocator.

Question 18. Can we call batch class from the trigger?

Answer – While we can call a batch class from the trigger, it is not advisable to do so. However, if we have to call it, we need to follow some considerations: Ensure that we do not call batch apex from the trigger each time. This is because of the reason that we can only have 5 apex jobs queued or executed at a time. Additionally, it should be bulkified to handle large columns of data

Question 19. How would you ensure that Batch Apex processes records efficiently and doesn’t hit governor limits?

Answer – Although the batch is used to avoid hitting the governor limit still there can be a chance that we might hit it.
The following things can be ensured to avoid hitting those limits:

1. Code optimization
2. DML withing loops
3. Process records in smaller batches

Question 20. Business Scenario:

Write a Batch Apex class to update the “OpportunityStage” field of all Opportunity records based on their “CloseDate”.

Answer – Below is the syntax to achieve the given scenarios

global class UpdateOpportunityStageBatch implements Database.Batchable<sObject> {
global Database.QueryLocator start(Database.BatchableContext BC) {
return Database.getQueryLocator([SELECT Id, CloseDate FROM Opportunity]);
}
global void execute(Database.BatchableContext BC, List<Opportunity> scope) {
for (Opportunity opp: scope) {
if (opp.CloseDate < Date.today()) {
opp.StageName = 'Closed Won';
} else {
opp.StageName = 'Prospecting';
}
}
update scope;
}
global void finish(Database.BatchableContext BC) {}
}