Describe the Common Performance Issues for User Interfaces and the Techniques to Mitigate Them. PLATFORM-DEVELOPER-II Practice Questions (Page 3)

Questions 11–15

1. 11application · medium

   A developer is optimizing a Lightning Web Component that renders a large table. The component updates the DOM for every record change, causing janky scrolling. Which technique should be used to improve client-side rendering performance?

   • AUse a JavaScript loop to update each row individually.
   • BUse a static resource for the data to avoid server calls.
   • CUse a virtual scrolling library to render only visible rows.
   • DUse a single large SOQL query to fetch all data at once.
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2. 12foundation · easy

   Which Salesforce platform feature helps improve UI performance by caching record data on the client?

   • AWorkflow rules
   • BLightning Data Service
   • CApex SOQL queries
   • DVisualforce pages
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4. 13expert · hard

   A developer is optimizing a Lightning Web Component that displays a complex dashboard with multiple charts and tables. The component uses several JavaScript libraries and performs heavy DOM manipulation. The page becomes unresponsive during initial load. Which approach would best improve the initial load performance?

   • ALoad all JavaScript libraries synchronously to ensure they are ready before rendering.
   • BLoad the JavaScript libraries asynchronously and defer non-critical rendering.
   • CUse a JavaScript framework that renders everything on the server.
   • DUse a single large JavaScript file to reduce the number of requests.
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5. 14application · medium

   A developer is building a Lightning component that performs a long-running server-side operation. The component currently waits for the operation to complete, causing the UI to freeze. Which technique should be used to keep the UI responsive?

   • AUse asynchronous Apex with @future or Queueable to run the operation in the background.
   • BUse a synchronous Apex call and show a loading spinner.
   • CUse a JavaScript setTimeout to delay the operation.
   • DUse a client-side loop to process the data.
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6. 15application · medium

   A developer notices that a Lightning component that displays a list of Opportunities is slow. The component uses a SOQL query that filters on a non-selective field. What is the most likely cause of the performance issue?

   • AThe query uses a subquery that is not indexed.
   • BThe query is not selective, causing a full table scan.
   • CThe query returns too many fields, causing a large payload.
   • DThe query uses a formula field in the WHERE clause.
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