Salesforce Lightning Interview Questions and Answers
Here are the Salesforce Lightning Interview Questions (Basic to Advanced – 2026)
Salesforce Lightning Interview Basic Level Questions & Answers
1. What is Salesforce Lightning ?
Salesforce Lightning is a modern UI framework for building responsive and dynamic applications on the Salesforce platform. It includes Lightning Experience, Lightning Web Components (LWC), and Lightning App Builder. It improves performance and user experience compared to Classic.
2. What is Lightning Web Components (LWC) ?
LWC is a modern programming model built using standard web technologies like HTML, JavaScript, and CSS. It leverages native browser features and Web Components standards. LWC provides better performance and cleaner architecture than Aura.
3. What is the difference between Aura and LWC ?
Aura is an older component framework, while LWC is built on modern JavaScript standards. LWC offers better performance, simpler syntax, and improved security. In 2026, LWC is the preferred development model.
4. What are the main files in an LWC component ?
An LWC bundle includes HTML (template), JavaScript (controller logic), and CSS (styling). It also includes a configuration XML file for metadata settings. These files work together as a reusable component.
5. What is @api decorator in LWC ?
@api makes a property or method public so it can be accessed by a parent component. It enables communication between components. It is mainly used for parent-to-child data passing.
6. What is @track in LWC? Is it still required in 2026 ?
@track was used to make properties reactive. In modern LWC versions, primitive fields are reactive by default, and @track is mainly needed for complex object reactivity in special cases.
7. What is @wire in LWC?
@wire is a decorator used to fetch Salesforce data reactively. It connects LWC to Apex methods or Salesforce data sources. It automatically refreshes when reactive parameters change.
8. What is Lightning Data Service (LDS) ?
LDS allows components to access and manipulate Salesforce records without writing Apex. It respects CRUD and FLS automatically and improves performance with shared caching.
9. How do you pass data from parent to child in LWC ?
Data is passed using public properties marked with @api in the child component. The parent binds values to those properties in the template.
10. How do you handle events in LWC ?
Events are handled using JavaScript event listeners. Custom events can be dispatched from child to parent using dispatchEvent().
Salesforce Lightning Interview Intermediate Level Questions & Answers
11. What is the difference between imperative Apex and @wire Apex ?
@wire is reactive and automatically runs when parameters change. Imperative Apex is called manually using JavaScript and gives better control over execution timing.
12. How do you make Apex calls from LWC ?
Import the Apex method into JavaScript and call it either using @wire or imperative method. The Apex method must be annotated with @AuraEnabled.
13. What are lifecycle hooks in LWC ?
Common lifecycle hooks include constructor(), connectedCallback(), renderedCallback(), and disconnectedCallback(). They control component initialization and rendering behavior.
14. What is renderedCallback() used for ?
renderedCallback() executes after the component is rendered in the DOM. It is useful for DOM manipulation or integrating third-party libraries.
15. How do you communicate between sibling components ?
Sibling components communicate using Lightning Message Service (LMS) or by sending events through a common parent component.
16. What are Custom Events in LWC ?
Custom Events allow child components to communicate with parents. They are created using new CustomEvent() and dispatched using dispatchEvent().
17. How do you handle form validation in LWC ?
Use standard Lightning input components with validation attributes. You can also use reportValidity() and custom validation logic in JavaScript.
18. What is Lightning Message Service (LMS) ?
LMS enables communication between components across DOM boundaries. It supports communication between LWC, Aura, and Visualforce.
19. How do you implement navigation in LWC ?
Use the NavigationMixin in LWC to navigate to records, objects, URLs, or apps. It ensures consistent navigation behavior in Lightning Experience.
20. How do you optimize LWC performance ?
Avoid unnecessary re-renders, use lazy loading, minimize Apex calls, and leverage LDS caching. Efficient state management improves performance.
Salesforce Lightning Interview Advanced Level Questions & Answers
21. How do you enforce CRUD and FLS in LWC ?
Use Lightning Data Service for automatic enforcement. For Apex calls, explicitly check permissions using Schema.sObjectType methods before processing data.
22. How do you secure Apex methods used in LWC ?
Use with sharing keyword and enforce CRUD/FLS checks. Avoid exposing sensitive data and validate inputs properly.
23. How do you handle large data sets in LWC data tables ?
Use pagination, lazy loading, and server-side processing. Avoid loading all records at once to prevent performance issues.
24. What is lazy loading in LWC ?
Lazy loading loads data only when needed instead of at initial render. It improves performance and reduces load time.
25. How do you implement reusable component architecture ?
Create modular components with configurable properties. Use separation of concerns and reusable utility classes for scalability.
26. How do you use Static Resources in LWC ?
Upload files like CSS, images, or JS libraries as Static Resources. Import them in LWC using @salesforce/resourceUrl.
27. How do you integrate third-party libraries in LWC ?
Upload the library as a Static Resource and load it using loadScript() in renderedCallback(). Ensure compatibility with Lightning security.
28. How does LWC support event-driven architecture in 2026 ?
LWC uses custom events, LMS, and Platform Events for real-time communication. This supports modern, loosely coupled architectures.
29. What are best practices for enterprise-level Lightning development ?
Follow component reusability, secure coding standards, proper error handling, and performance optimization. Maintain clean architecture and high test coverage.
30. How is AI (Einstein + Copilot) impacting Lightning development in 2026 ?
AI tools assist in auto-generating components, improving UI personalization, and suggesting optimized code. Developers now focus more on architecture and integration strategy.
2026 Trend-Based Questions
1. How is Salesforce AI (Einstein Copilot) transforming Lightning Web Component development in 2026 ?
Einstein Copilot transforms LWC development by auto-generating code, improving UI personalization, and assisting with intelligent component design.
2. When should you use Lightning Message Service over traditional component communication patterns ?
Lightning Message Service should be used when components need to communicate across DOM boundaries or between LWC, Aura, and Visualforce.
3. How do you design high-performance LWCs for enterprise-level large data volumes ?
High-performance LWCs for large data volumes require pagination, lazy loading, server-side processing, and minimal re-rendering.
4. How do you implement secure, scalable component architecture in modern Lightning applications ?
Secure and scalable component architecture is achieved using reusable components, separation of concerns, and strict CRUD/FLS enforcement.
5. How is event-driven architecture influencing Lightning development in 2026 ?
Event-driven architecture influences Lightning development by enabling real-time communication using LMS, Platform Events, and asynchronous processing.
Summary
- In 2026, Salesforce Lightning development focuses on performance, scalability, security, and AI-driven innovation. Lightning Web Components (LWC) remain the standard UI framework, leveraging modern web standards for faster and more efficient applications.
- Interviewers expect strong knowledge of component communication (LMS, custom events), lifecycle hooks, Apex integration, CRUD/FLS security enforcement, and large data handling strategies. Additionally, understanding event-driven architecture and enterprise-level reusable component design is essential.
- With the rise of Einstein Copilot and AI-powered automation, developers are now expected to combine technical expertise with smart architecture decisions to build secure, high-performance, and future-ready Lightning applications.
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