Top 10 Salesforce Interview Questions and Answers (Apex, Lightning & Integration)

Preparing for a Salesforce developer or technical architect interview requires mastering both core declarative mechanics and programmatic architecture. Here is a breakdown of 10 essential interview questions covering data modeling, asynchronous Apex, event-driven architecture, and UI frameworks.

In plain words: Salesforce technical interviews test your understanding of governor limits, secure integrations, event handling, and data relationships—focusing on when to use declarative configuration versus programmatic code.

1. Data Architecture: Junction Objects

Question: What is a Junction Object in Salesforce?

A Junction Object is a custom object with two Master-Detail relationship fields. It creates a many-to-many relationship between two parent objects.

Real-Life Example: In a hiring app, one Candidate can apply for multiple Positions, and one Position receives applications from multiple Candidates. The custom object JobApplication__c acts as the junction object linking them together.

2. Event-Driven Architecture: Platform Events

Question: What is a Platform Event, and why do we use it?

Platform Events enable enterprise event-driven messaging on the Salesforce platform based on a Publish/Subscribe architecture. Instead of tightly coupled point-to-point API calls, Salesforce and external systems publish messages to the event bus and subscribers process them in near real-time.

• Publish events in Apex using the EventBus.publish() method.
• Listen to and process events via Flows, Apex triggers, or external streaming clients (Pub/Sub API / CometD).
• Decouples integrations so system changes do not cause hard failures across connected applications.

3. Asynchronous Apex: Queueable Interface

Question: What is Queueable Apex, and how is it used?

Queueable Apex is an asynchronous processing mechanism that extends the capabilities of @future methods. It allows you to submit jobs to the Salesforce queue, monitor their execution, pass complex data types (such as sObjects or custom classes), and chain sequential jobs together.

// Defining a Queueable class
public class ProcessAccountSync implements Queueable {
    public void execute(QueueableContext context) {
        // Business logic or asynchronous processing
    }
}

// Enqueueing the job and chaining
Id jobId = System.enqueueJob(new ProcessAccountSync());

4. Apex Unit Testing: Test.startTest() and Test.stopTest()

Question: What is the purpose of Test.startTest() and Test.stopTest()?

These methods define the exact execution window for the code you are testing. They provide two major capabilities:

• Governor Limit Reset: Code executed between Test.startTest() and Test.stopTest() gets a fresh, isolated set of governor limits separate from your test data setup.
• Synchronous Execution: Calling Test.stopTest() forces all enqueued asynchronous processes (such as Batch, Queueable, or Future jobs) to finish execution before test assertions run.

5. Lightning Components: Calling Apex Actions

Question: How do you invoke an Apex controller method from a Lightning component?

In the legacy Aura framework, server methods are instantiated, parameterized, assigned callbacks, and added to the action queue. In modern Lightning Web Components (LWC), methods are imported directly as ES6 modules and invoked using either the @wire decorator or JavaScript Promises.

// Modern LWC Imperative Apex Call
import getAccounts from '@salesforce/apex/AccountController.getAccounts';

export default class AccountList extends LightningElement {
    handleLoad() {
        getAccounts({ industry: 'Technology' })
            .then(result => {
                this.accounts = result;
            })
            .catch(error => {
                console.error('Error fetching accounts:', error);
            });
    }
}

6. Framework Queue: $A.enqueueAction()

Question: What is the purpose of $A.enqueueAction()?

In Aura components, $A.enqueueAction(action) adds a server-side controller call to the framework's internal action queue. Rather than opening separate HTTP connections for every request, Salesforce batches these enqueued actions together and sends them to the server at the end of the event cycle.

7. Integration: Remote Site Settings vs. Named Credentials

Question: What is the difference between Remote Site Settings and Named Credentials?

Integration Security Comparison:

• Remote Site Settings: Whitelists external endpoint URLs so Apex can make HTTP callouts. It handles zero authentication—developers must manage headers, tokens, and credentials manually in code.
• Named Credentials: Encapsulates both the endpoint URL and authentication configurations (OAuth, Basic Auth, AWS Signature v4). Salesforce automatically handles headers and token refreshing, eliminating hardcoded secrets from Apex code.

Security Trap: Never store API keys, usernames, or passwords in Apex code or standard custom fields. Always use Named Credentials or External Credentials to secure external service integrations.

8. Configuration Architecture: Custom Settings vs. Custom Metadata Types

Question: What is the key difference between Custom Settings and Custom Metadata Types?

• Custom Settings: Treated as database records (data). Hierarchy types let you vary configurations per user or profile, but their records cannot be deployed directly via change sets or metadata packages without data migration tools.
• Custom Metadata Types (CMDT): Treated as metadata. Both the schema and the configuration records are deployed directly through CI/CD pipelines, Git, and change sets without requiring data loading scripts.

9. Event Propagation: Lightning Event Phases

Question: What are the event propagation phases in the Lightning Component framework?

• Capture Phase: The event propagates downwards from the top parent application/component down to the source component that fired it.
• Bubble Phase: The event propagates upwards from the component that fired the event up through the containment hierarchy to the top-level parent.

10. Aura Architecture: Value Providers

Question: What are Value Providers in Aura?

Value providers encapsulate data and methods within an Aura component, defining their scope and access level:

• c (Controller / Action Provider): References client-side JavaScript controllers or server-side Apex actions (e.g., {!c.handleClick}).
• v (View / Attribute Provider): Accesses component attributes and view-state variables declared in markup (e.g., {!v.recordId}).

Core Rule: When designing scalable solutions, prioritize Custom Metadata Types over Custom Settings, use Named Credentials for callouts, and write asynchronous logic with Queueable Apex.