11. What is the maximum batch size you can set?

Maximum batch size: 2,000 records

12. What is the minimum batch size?

Minimum batch size: 1 record

13. What is the default batch size?

Default batch size: 200 records (if not specified when calling Database.executeBatch())

14. What is the Apex Flex Queue?

The Apex Flex Queue holds batch jobs in a “Holding” status when the 5 concurrent execution slots are full. It can store up to 100 batch jobs waiting to be executed.

15. What is the maximum capacity of the Apex Flex Queue?

100 batch jobs can be held in the Apex Flex Queue at any time.

73. What advantages does Queueable Apex have over Future Methods?

Queueable Apex offers several improvements:

• Non-primitive types: Can pass SObjects and custom Apex types
• Monitoring: Returns a job ID for tracking via AsyncApexJob
• Job chaining: Can chain jobs for sequential processing
• Better structure: More organized with the Queueable interface

Id jobId = System.enqueueJob(new MyQueueableClass());
// Track progress
AsyncApexJob jobInfo = [
    SELECT Id, Status, NumberOfErrors 
    FROM AsyncApexJob 
    WHERE Id = :jobId
];

74. Which interface is used for Queueable Apex?

The Queueable interface.

75. What methods are required in Queueable Apex?

Only the execute(QueueableContext context) method is required.

76. How many jobs can you chain from a Queueable job?

You can add only one child job per parent job to avoid excessive nesting.

77. How many Queueable jobs can you enqueue in one transaction?

You can add up to 50 jobs to the queue using System.enqueueJob() in a single transaction.

78. How do you use the job ID to track a Queueable job?

Query the AsyncApexJob object:

AsyncApexJob jobInfo = [
    SELECT Status, NumberOfErrors 
    FROM AsyncApexJob 
    WHERE Id = :jobID
];

79. Can you make callouts from Queueable jobs?

Yes, implement the Database.AllowsCallouts interface:

public class MyQueueable implements Queueable, Database.AllowsCallouts {
    public void execute(QueueableContext context) {
        // Make HTTP callouts
    }
}

80. What happens if you call System.enqueueJob() multiple times?

After 50 calls in one transaction, you’ll get: “LimitException: Too many queueable jobs added to the queue: 51”

81. What are Queueable Apex limitations?

• Maximum 50 jobs per transaction
• Maximum chain depth of 5 (4 child jobs + 1 parent) in Developer/Trial orgs
• Cannot chain Queueable jobs in test methods

82. Write a Queueable Apex blueprint

public class MyQueueableClass implements Queueable {
    private List<Id> recordIds;
    
    public MyQueueableClass(List<Id> ids) {
        this.recordIds = ids;
    }
    
    public void execute(QueueableContext context) {
        // Process records
        List<Account> accounts = [
            SELECT Id, Name 
            FROM Account 
            WHERE Id IN :recordIds
        ];
        // Update logic here
    }
}

83. What is QueueableContext?

An interface implemented internally by Apex that contains the job ID. Access it via context.getJobId():

public void execute(QueueableContext context) {
    Id jobId = context.getJobId();
}

84. How do you enqueue a Queueable job?

Id jobId = System.enqueueJob(new MyQueueableClass());

85. How do you process 200 records in batches of 100 using Queueable Apex?

Queueable Apex doesn’t support batch processing like Batch Apex. It processes all records in a single execution context. Consider using Batch Apex for true batching.

86. Can you chain a job with callouts from one without?

Yes, callouts are allowed in chained Queueable jobs.

87. How do you test Queueable chaining?

You cannot chain Queueable jobs in tests. Write separate test methods for each chained job and add Test.isRunningTest() checks:

public void execute(QueueableContext context) {
    // Process current job
    
    if (!Test.isRunningTest()) {
        System.enqueueJob(new NextQueueableJob());
    }
}

88-100. Additional Queueable Interview Questions

[Content continues with more advanced Queueable scenarios…]

121. Scenario: Nightly synchronization of opportunities with external system (Marketo)

Solution: Use Scheduled Batch Apex

1. Scheduler schedules the batch to run nightly
2. Start Method: Query opportunities updated in last 24 hours
3. Execute Method: Make callouts to Marketo for each batch
4. Finish Method: Send summary email

global class OpportunitySyncBatch implements Database.Batchable<sObject>, Database.AllowsCallouts, Database.Stateful {
    global Integer successCount = 0;
    global Integer failCount = 0;
    
    global Database.QueryLocator start(Database.BatchableContext bc) {
        return Database.getQueryLocator([
            SELECT Id, Name, Amount, StageName 
            FROM Opportunity 
            WHERE LastModifiedDate = LAST_N_DAYS:1
        ]);
    }
    
    global void execute(Database.BatchableContext bc, List<Opportunity> scope) {
        for(Opportunity opp : scope) {
            try {
                syncToMarketo(opp);
                successCount++;
            } catch(Exception e) {
                failCount++;
            }
        }
    }
    
    global void finish(Database.BatchableContext bc) {
        sendSummaryEmail(successCount, failCount);
    }
}

Why not Data Loader?

• Requires manual intervention
• No automation capabilities
• Limited error handling
• Cannot make API callouts

122. When to use Batch Apex instead of Queueable Apex?

Use Batch Apex for:

• Processing millions of records
• Need to chunk data into manageable batches
• Higher governor limits required

Use Queueable Apex for:

• Near real-time processing
• Smaller datasets
• Need to pass complex objects
• Require job chaining

123. Scenario: Real-time order synchronization with ShipStation

Solution: Use Queueable Apex triggered from Order trigger

trigger OrderTrigger on Order (after insert, after update) {
    for(Order ord : Trigger.new) {
        System.enqueueJob(new SyncOrderToShipStation(ord.Id));
    }
}

public class SyncOrderToShipStation implements Queueable, Database.AllowsCallouts {
    private Id orderId;
    
    public SyncOrderToShipStation(Id ordId) {
        this.orderId = ordId;
    }
    
    public void execute(QueueableContext context) {
        Order ord = [SELECT Id, OrderNumber, TotalAmount FROM Order WHERE Id = :orderId];
        // Make callout to ShipStation
        syncToShipStation(ord);
    }
}

Why Queueable over Batch/Future?

• Near real-time processing (immediately after order creation)
• Can pass complex objects
• Better monitoring than Future Methods
• Supports job chaining for multi-step processes

124. Database.QueryLocator vs Iterable

Database.QueryLocator:

• Processes up to 50 million records
• Uses SOQL queries
• Ideal for Salesforce data

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

Iterable:

• Processes up to 50,000 records
• More flexible for external data sources
• Custom logic for data retrieval

global Iterable<Account> start(Database.BatchableContext bc) {
    List<Account> accounts = getAccountsFromExternalSystem();
    return accounts;
}

125. How do you schedule a Batch Apex job?

Two methods:

Method 1: System.scheduleBatch()

String cronExp = '0 0 1 * * ?'; // 1 AM daily
MyBatchClass batch = new MyBatchClass();
System.scheduleBatch(batch, 'Nightly Batch Job', 60); // 60-minute delay

Method 2: Schedulable Apex + Database.executeBatch()

global class ScheduleBatch implements Schedulable {
    global void execute(SchedulableContext sc) {
        Database.executeBatch(new MyBatchClass(), 200);
    }
}
System.schedule('Daily Batch', '0 0 1 * * ?', new ScheduleBatch());