LWCAdvancedimperativeerror-handlingux
Implement optimistic UI update with rollback on Apex validation failure
Real World Scenario
Task completion checkbox toggles instantly but Apex validation fails leaving checkbox checked while task still open.
Expected Answer
• Clone prior state before optimistic UI update
• On Apex error restore clone state to checkbox and row styling
• Disable control during in-flight request preventing double toggle
• Show field-level error from AuraHandledException body
• Optimistic only for low-risk UI; financial toggles wait server confirm
• Jest test error path asserts UI reverts to prior state
• LDS notify only on confirmed success not optimistic step
Follow-Up Questions & Answers
Click to expand — each follow-up includes a direct, interview-ready answer
Main difference: use case and scale. Clone prior state before optimistic UI update. On Apex error restore clone state to checkbox and row styling. Pick based on your integration pattern and team capability. Optimistic UI must include rollback path—otherwise error handling worse than spinner. Optimize for scale and operational observability.
Architect Perspective
Optimistic UI must include rollback path—otherwise error handling worse than spinner.