Top 40+ Apex Interview Questions and Answers- Basic to Advance

Are you preparing for an Apex interview? To help you out, we have compiled over 40 interview questions for Salesforce Apex, along with comprehensive answers to help you prepare effectively. This guide covers key concepts such as Governor Limits, Apex Triggers, and Batch Apex, as well as advanced topics like Dynamic Apex, REST API implementation, and handling exceptions. 

Apex Interview Questions with Detailed Answers

1. What is Apex?
2. Explain Governor Limits in Apex.
3. What are Apex Triggers?
4. Describe the difference between SOQL and SOSL.
5. What is Batch Apex?
6. Explain how you would implement error handling in Batch Apex.
7. What is Dynamic Apex?
8. How do you optimize SOQL queries in Apex?
9. What are the best practices for writing maintainable Apex code?
10. Describe how you would manage governor limits in complex applications.
11. How do you handle exceptions in Apex?
12. What is Queueable Apex?
13. Explain how you would implement a REST API using Apex.
14. What strategies do you use for testing your Apex code?
15. How do you secure your Apex code?
16. Describe how you would perform data migration using Apex.
17. What are Custom Metadata Types?
18. How do you debug your Apex code?
19. Explain what an Abstract Class is in Apex.
20. How do you ensure efficient API callouts?
21. What is a Future Method in Apex, and when would you use it?
22. Explain the concept of @InvocableMethod and @InvocableVariable in Apex.
23. How would you use Custom Settings in Apex, and what are their benefits?
24. Describe how you would use an Interface in Apex and provide an example.
25. What is a Custom Exception in Apex, and how do you create one?
26. How do you handle DML operations in Apex with a large number of records?
27. What is the Map data type in Apex, and when is it most useful?
28. Explain what System.LimitException is in Apex and how to avoid it.
29. How do you implement pagination in Apex?
30. What is the purpose of Apex Managed Sharing?
31. Describe how you would use System.runAs() in Apex and why it’s important.
32. What are the WITH SECURITY_ENFORCED and WITH SHARING keywords in Apex?
33. How does Apex handle transaction control, and what are SAVEPOINT and ROLLBACK?
34. What is the purpose of @TestSetup in Apex test classes?
35. Explain the difference between Database.executeBatch and Queueable Apex.
36. What is the benefit of using Set collections in Apex, and how do you handle duplicates?
37. How do you perform custom validation on data before insert or update in Apex?
38. Explain how you would monitor asynchronous Apex jobs.
39. How does @ReadOnly annotation improve performance in Apex?
40. Describe the difference between before and after triggers in Apex.

1. What is Apex?

Answer:

Apex is a strongly typed, object-oriented programming language that allows developers to execute flow and transaction control statements on the Salesforce platform’s server in conjunction with calls to the API. It is designed to be easy to use and integrates seamlessly with the Salesforce database. Apex can be used to create custom business logic, automate processes, and handle complex data manipulations.

2. Explain Governor Limits in Apex.

Answer: Governor limits are runtime limits enforced by Salesforce to ensure that no single customer monopolizes shared resources. These limits apply to various operations, including:

• SOQL Queries: A maximum of 100 SOQL queries can be executed in a single transaction.
• DML Statements: Up to 150 DML operations are allowed per transaction.
• Heap Size: The maximum heap size for synchronous transactions is 6 MB, while for asynchronous transactions, it’s 12 MB.
• Callouts: A maximum of 100 callouts (HTTP requests or web service calls) can be made in a single transaction.

Understanding and adhering to these limits is crucial for developing efficient and scalable applications on the Salesforce platform.

3. What are Apex Triggers?

Answer:

Apex triggers are pieces of code that execute before or after specific data manipulation language (DML) events occur on Salesforce records. Triggers can be used for:

• Before Triggers: To perform operations before a record is saved (e.g., validation).
• After Triggers: To perform operations after a record has been saved (e.g., sending notifications).

Triggers should be bulkified to handle multiple records efficiently and avoid hitting governor limits.

4. Describe the difference between SOQL and SOSL.

Answer: SOQL (Salesforce Object Query Language) and SOSL (Salesforce Object Search Language) are both used to query data in Salesforce but serve different purposes:

• SOQL: Used to retrieve records from a single object or related objects. It allows filtering of records using WHERE clauses. Example:

  SELECT Id, Name FROM Account WHERE Industry = 'Technology'

• SOSL: Used to search across multiple objects simultaneously. It returns records from multiple objects based on search terms. Example:

  FIND {searchString} IN ALL FIELDS RETURNING Account(Id, Name), Contact(Id, Name)

5. What is Batch Apex?

Answer: Batch Apex is a way to process large volumes of records asynchronously in manageable chunks. It implements the Database.Batchable interface and allows you to define three methods:

• start(): Used to collect the records or objects to be processed.
• execute(): Contains the logic that processes each batch of records.
• finish(): Executes after all batches have been processed, often used for final operations like sending notifications.

Using Batch Apex helps avoid governor limits by processing records in smaller batches.

6. Explain how you would implement error handling in Batch Apex.

Answer:

Error handling in Batch Apex can be implemented by using the Database.Stateful interface, which allows you to maintain state across batch executions. You can also catch exceptions within the execute() method and log errors accordingly:

global class MyBatchClass implements Database.Batchable<SObject>, Database.Stateful {
    global Database.QueryLocator start(Database.BatchableContext BC) {
        return Database.getQueryLocator('SELECT Id FROM Account');
    }

    global void execute(Database.BatchableContext BC, List<SObject> scope) {
        try {
            // Processing logic here
        } catch (Exception e) {
            // Log error details
        }
    }

    global void finish(Database.BatchableContext BC) {
        // Finalize process
    }
}

7. What is Dynamic Apex?

Answer:

Dynamic Apex refers to the ability of Apex code to adapt at runtime by using dynamic features such as reflection. This allows developers to work with sObjects and fields without knowing their structure at compile time. Use cases include:

• Creating generic code that can handle different object types.
• Accessing metadata about objects dynamically using Schema methods.

Example:

String sObjectName = 'Account';
SObject obj = Schema.getGlobalDescribe().get(sObjectName).newSObject();
obj.put('Name', 'New Account');
insert obj;

8. How do you optimize SOQL queries in Apex?

Answer: Optimizing SOQL queries involves several techniques:

• Select Only Necessary Fields: Avoid using SELECT * and specify only the fields needed.
• Use WHERE Clauses: Filter records as much as possible using conditions.
• Avoid Queries Inside Loops: Move SOQL outside of loops to prevent multiple queries from executing unnecessarily.
• Utilize Indexed Fields: Use indexed fields in your WHERE clauses for faster query performance.

9. What are the best practices for writing maintainable Apex code?

Answer: To ensure maintainability of Apex code, consider the following best practices:

• Modular Code Design: Break code into smaller, reusable classes and methods.
• Consistent Naming Conventions: Use clear and descriptive names for classes, methods, and variables.
• Commenting and Documentation: Provide comments explaining complex logic and document your code structure.
• Unit Testing: Write comprehensive test classes with at least 75% code coverage to ensure functionality remains intact during changes.

10. Describe how you would manage governor limits in complex applications.

Answer: Managing governor limits requires careful planning and coding practices:

• Bulkify Code: Ensure that your code can handle multiple records at once instead of one at a time.
• Use Asynchronous Processing: Utilize Batch Apex or Queueable Apex for long-running processes that may exceed limits.
• Optimize Queries and DML Operations: Minimize the number of SOQL queries and DML statements by consolidating operations where possible.

11. How do you handle exceptions in Apex?

Answer: Exception handling in Apex is done using try-catch blocks:

try {
    // Code that may throw an exception
} catch (Exception e) {
    // Handle exception
    System.debug('Error occurred: ' + e.getMessage());
}

This approach allows developers to manage errors gracefully without crashing the application, providing opportunities for logging or alternative flows when exceptions occur.

12. What is Queueable Apex?

Answer: Queueable Apex is a way to run asynchronous jobs in Salesforce that allows you to chain jobs together. It implements the Queueable interface which provides more flexibility than future methods:

• You can pass complex objects between jobs.
• You can chain jobs by calling another queueable job from within an existing one.

Example:

public class MyQueueableJob implements Queueable {
    public void execute(QueueableContext context) {
        // Job logic here
    }
}

// Enqueueing a job
System.enqueueJob(new MyQueueableJob());

13. Explain how you would implement a REST API using Apex.

Answer: To implement a REST API in Salesforce using Apex, you need to create an Apex class annotated with @RestResource. This class will define HTTP methods like GET, POST, PUT, DELETE for handling requests:

@RestResource(urlMapping='/myapi/*')
global with sharing class MyRestResource {
    @HttpGet
    global static MyResponseType doGet() {
        // Logic for GET request
    }

    @HttpPost
    global static MyResponseType doPost(MyRequestType requestBody) {
        // Logic for POST request
    }
}

This setup allows external systems to interact with Salesforce data via RESTful calls.

14. What strategies do you use for testing your Apex code?

Answer: Testing strategies include:

• Unit Tests: Write unit tests for every piece of logic you develop, ensuring at least 75% coverage.
• Test Data Creation: Create test data within test methods using @isTest annotation without relying on actual data from your org.
• Assertions: Use assertions (System.assertEquals, System.assertNotEquals) to validate expected outcomes against actual results during tests.

15. How do you secure your Apex code?

Answer: Security measures include:

• Field-Level Security: Always check field-level security before accessing fields in your code.
• Sharing Rules: Use sharing rules appropriately when querying or manipulating data to respect user permissions.
• Named Credentials: Use Named Credentials for secure storage of authentication details when making callouts to external systems.

16. Describe how you would perform data migration using Apex.

Answer: Data migration can be performed using Batch Apex or Data Loader tools depending on volume:

1. For large datasets, create a Batch class that processes records in chunks.
2. For smaller datasets or one-time migrations, consider using Data Loader or custom scripts that leverage Bulk API capabilities.
3. Ensure data integrity by validating records before insertion/updating during migration processes.

17. What are Custom Metadata Types?

Answer: Custom Metadata Types allow developers to create custom sets of data that can be deployed between environments (like sandboxes). They are similar to custom settings but offer more flexibility:

• They support relationships with other metadata types.
• Custom metadata records can be queried without hitting governor limits like standard object queries do.

Example:

List<MyCustomMetadata__mdt> metadataRecords = [SELECT MasterLabel FROM MyCustomMetadata__mdt];

18. How do you debug your Apex code?

Answer: Debugging can be accomplished through several methods:

• Debug Logs: Set up debug logs via Setup > Debug Logs where you can monitor execution details.
• System.debug() Statements: Insert debug statements within your code to output variable values at runtime.
• Apex Replay Debugger: Use this tool in Visual Studio Code or Developer Console for advanced debugging capabilities, allowing step-through debugging of past executions based on logs captured earlier.

19. Explain what an Abstract Class is in Apex.

Answer: An abstract class in Apex cannot be instantiated directly but provides a base class from which other classes can inherit. It may contain abstract methods (without implementation) that must be defined in derived classes:

public abstract class Animal {
    public abstract void makeSound();
}

public class Dog extends Animal {
    public override void makeSound() {
        System.debug('Bark');
    }
}

This structure promotes code reuse and enforces a contract for subclasses implementing specific behaviors.

20. How do you ensure efficient API callouts?

Answer: To ensure efficient API callouts:

1. Limit callouts within loops; instead batch requests where possible.
2. Monitor response times and handle failures gracefully using try-catch blocks.
3. Utilize Named Credentials for managing authentication securely without hardcoding credentials into your codebase.
4. Implement caching strategies if applicable, reducing unnecessary repeated calls for frequently accessed data.

21. What is a Future Method in Apex, and when would you use it?

Answer:

Future methods are asynchronous Apex methods that allow for processes to be run in the background. They are useful for long-running operations and operations that don’t need to be completed immediately, such as making external web service callouts from a trigger. Future methods are annotated with @future and are particularly beneficial in reducing execution time in synchronous contexts, especially for operations that involve callouts or heavy data processing.

22. Explain the concept of @InvocableMethod and @InvocableVariable in Apex.

Answer:

@InvocableMethod and @InvocableVariable annotations allow you to expose Apex methods and variables to be accessible through Flow and Process Builder, making them useful for administrators and business analysts. The @InvocableMethod annotation is used on a static method that can be called from a Flow, allowing for complex logic to be encapsulated in Apex and triggered through declarative tools. @InvocableVariable is used to make variables in the method accessible to the Flow, supporting flexibility in data manipulation and business process automation.

23. How would you use Custom Settings in Apex, and what are their benefits?

Answer:

Custom settings in Apex allow you to store static data in Salesforce that is accessible across all users and can be used to store application configurations. Custom settings are beneficial because they reduce the need to hardcode values, and they improve performance as their data is cached. There are two types of custom settings: List Custom Settings (shared values across all users) and Hierarchy Custom Settings (can have user-specific or profile-specific values).

24. Describe how you would use an Interface in Apex and provide an example.

Answer:

In Apex, an interface is a collection of method definitions that must be implemented by any class that implements the interface. Interfaces are useful for defining methods that can be customized in multiple ways by different classes. For example, you might create an interface ISendNotification with a method sendMessage(), which can then be implemented by different classes to send messages via email, SMS, or in-app notifications.

25. What is a Custom Exception in Apex, and how do you create one?

Answer:

A custom exception is a user-defined exception class in Apex, useful for creating specific error messages for different failure scenarios in your code. Custom exceptions are created by extending the Exception class. For instance:

   public class InvalidAccountTypeException extends Exception {}

This allows for more granular control over error handling and can improve the clarity of error messages during debugging and user interaction.

26. How do you handle DML operations in Apex with a large number of records?

Answer:

When dealing with large data volumes, it is important to avoid exceeding governor limits. Use Database.insert, Database.update, and similar methods with allOrNone=false to allow partial success in DML operations. Additionally, batching large datasets or using asynchronous methods like Batch Apex is recommended. For example, Database.update(accounts, false) allows failed records to be logged without halting the operation.

27. What is the Map data type in Apex, and when is it most useful?

Answer:

The Map data type is a collection that stores key-value pairs, where each key is unique. Maps are highly efficient for quick lookups, especially useful when handling records identified by unique fields, such as IDs or names. Maps are particularly effective in avoiding repetitive SOQL calls in a loop by retrieving records once and storing them in the map for easy access.

28. Explain what System.LimitException is in Apex and how to avoid it.

Answer:

System.LimitException occurs when your Apex code exceeds one of Salesforce’s governor limits, such as SOQL query limits, DML statement limits, or CPU time limits. To avoid it, always use best practices like limiting SOQL queries within loops, using batch processes, and leveraging caching techniques. Proper exception handling and bulk processing methods like @future, Queueable, and Batch Apex can also help.

29. How do you implement pagination in Apex?

Answer:

Pagination is implemented using SOQL OFFSET or Apex StandardSetController in Visualforce, allowing users to navigate large datasets efficiently. Using OFFSET in SOQL queries enables skipping a specified number of rows, although it is limited to 2,000 rows. For larger datasets, the StandardSetController is preferable, as it provides built-in pagination with first, next, previous, and last methods.

30. What is the purpose of Apex Managed Sharing?

Answer:

Apex Managed Sharing allows you to programmatically create and manage sharing rules for records. It is used when standard sharing settings do not meet business requirements. Managed sharing can be implemented using Share objects, which allow developers to control which users or groups have access to specific records, typically in scenarios where record-level security is complex.

31. Describe how you would use System.runAs() in Apex and why it’s important.

Answer:

System.runAs() allows you to execute code as a different user in test methods. It’s important for testing scenarios involving different user permissions or sharing settings. runAs helps simulate different roles and profiles, ensuring that code respects user permissions, which is crucial for testing compliance with security requirements.

32. What are the WITH SECURITY_ENFORCED and WITH SHARING keywords in Apex?

Answer:

WITH SECURITY_ENFORCED in SOQL ensures that field-level security and object permissions are enforced during query execution, raising an error if the user does not have access. WITH SHARING in class definitions respects record sharing rules for the user executing the code, ensuring that users only see records they have access to. These keywords are crucial for enforcing security best practices in multi-user environments.

33. How does Apex handle transaction control, and what are SAVEPOINT and ROLLBACK?

Answer:

Apex provides transaction control with SAVEPOINT and ROLLBACK, allowing you to define points in the transaction to which you can revert if needed. SAVEPOINT marks a point in the transaction, and ROLLBACK returns the transaction to that point, which is useful in complex operations where partial failures should not commit changes.

34. What is the purpose of @TestSetup in Apex test classes?

Answer:

@TestSetup allows you to create reusable test data for all test methods within a test class. It executes only once per test run, optimizing test execution time. This annotation is valuable for creating common data that does not need to be duplicated in every test method, ensuring cleaner and more efficient test code.

35. Explain the difference between Database.executeBatch and Queueable Apex.

Answer:

Database.executeBatch is for large data processing tasks that can be divided into smaller chunks and executed in a batch. Queueable Apex is more flexible and ideal for chaining asynchronous tasks, but it cannot process as many records as Batch Apex. Queueable Apex also supports complex objects and has higher heap size limits.

36. What is the benefit of using Set collections in Apex, and how do you handle duplicates?

Answer:

Set collections store unique values and are beneficial for filtering duplicates, as sets automatically discard duplicate values. Set is ideal for scenarios where you need distinct records, such as when processing records with unique IDs.

37. How do you perform custom validation on data before insert or update in Apex?

Answer:

Custom validation in Apex can be performed within triggers or before performing DML operations by using conditional statements. You can raise exceptions with specific messages if data does not meet the conditions, which helps maintain data integrity and prevent faulty records.

38. Explain how you would monitor asynchronous Apex jobs.

Answer:

Asynchronous jobs can be monitored through the Apex Jobs page in Salesforce Setup, which lists job statuses, start times, and completion details. Additionally, you can use System.enqueueJob to obtain job IDs programmatically, allowing you to track job progress using SOQL queries on the AsyncApexJob object.

39. How does @ReadOnly annotation improve performance in Apex?

Answer:

The @ReadOnly annotation allows you to retrieve up to 1 million rows in a Visualforce page without exceeding governor limits. This annotation is valuable for read-only data reporting in Visualforce pages, as it optimizes performance by not counting SOQL rows against governor limits.

40. Describe the difference between before and after triggers in Apex.

Answer:

In Apex, before triggers are used for tasks that need to be completed before data is committed to the database, such as validation or setting default values. after triggers execute once the data has been saved, and they are typically used for actions dependent on database values, like updating related records or performing calculations.

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