FrontendHaltReact·Intermediate·Conceptual·1 min read
Is a re-render always expensive?
Short interview answer
No. A re-render that produces the same output and requires no DOM mutation is usually cheap. The real cost to worry about is expensive computation happening during that render, or an actual DOM/layout change caused by it — not the render call itself.
Key takeaway
Explain the underlying mental model clearly, then support it with a concrete example and its trade-offs.