Question 1

List key Angular performance techniques.

Accepted Answer

OnPush/signals, lazy routes, track in @for, defer blocks, virtual scroll, and avoiding heavy template methods. Measure with Angular DevTools profiler. Optimize network and bundle size too—perf is not only CD.

Question 2

What is @defer and when do you use it?

Accepted Answer

Defers loading a template block until a trigger (idle, viewport, interaction), reducing initial work. Great for below-the-fold widgets. Provide @placeholder/@loading/@error. Don't defer critical above-the-fold UI.

Question 3

How does CDK virtual scrolling help?

Accepted Answer

Renders only visible list items, keeping DOM small for large datasets. Requires item size strategy. Combine with trackBy/track. Not a substitute for pagination on huge server lists.

Question 4

How do you diagnose unnecessary change detection cycles?

Accepted Answer

Use profiler to see frequent checks; look for impure pipes, template methods, and noisy Zone events. Switch to OnPush/signals, debounce high-frequency events, run outside Angular when appropriate.

Question 5

What bundle strategies help Angular apps load faster?

Accepted Answer

Lazy routes, deferrable views, treeshakeable providers, and analyzing with source-map-explorer. Avoid importing large libraries in root. Prefer standalone imports of only needed pieces.

Question 6

Is pure pipe caching enough for expensive list transforms?

Accepted Answer

Helps when inputs are referentially stable; still prefer precomputing in computed signals for complex views. Impure pipes run every CD—avoid. For filtered lists, compute in the class with signals.

Performance Angular Interview Questions

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