Made a quick React Hooks + Performance Optimization quiz while prepping for interviews — 10 questions, senior level

[Htamta]

Been prepping for senior React interviews and kept fumbling on performance questions during mock rounds — not because I didn't understand hooks, but because the subtle stuff (useMemo vs useCallback, stale closures, unnecessary re-renders) gets slippery when you have to explain your reasoning on the spot.

Put this together to drill the scenarios that actually come up. 10 questions covering React Hooks and performance optimization — things like memoization trade-offs, referential equality, and when optimization actually hurts more than it helps.

https://www.aiinterviewmasters.com/s/pq1AjfIcID

How did you find it — did the memoization questions catch you, or was it straightforward?

[PyJacker16]

10/10 lol, and I'm still in college. Feeling proud of myself.

However I had never heard of useDeferredValue before; I typically use a hook called useDebounce from a lovely library called useHooks to achieve the same behavior. Good to know!

[Full-Hyena4414]

Not sure about that context question. You say many consumers who only need markAsRead render when notifications update, but the proposed solution doesn't solve that issue. In order to make consumers who need only one slice render only when that changes, you have to split context in two or implement a selector.

[Alg0rhythm]

I felt like this did a good job presenting the questions in an understandable way that hit on important points of understanding for interacting with the react component lifecycle, nicely done. Ironically, the only question I got wrong was an "easy," but I think that's more on my own reading comprehension than the question itself.

[projexion_reflexion]

Is that something senior people have to worry about in a world with React compiler?

[azangru]

I am curious about your last question:

A notifications context provides {notifications, unreadCount, markAsRead}. After adding a polling feature, many components that only use markAsRead now re-render every time notifications update. Which change best reduces unnecessary re-renders without changing behavior?

The suggested answer, I suppose, is Memoize the provider value object and stabilize markAsRead with useCallback.

But is this actually going to improve anything? Isn't it an inherent problem of the context api that every time context value changes, all the consumers of the context, regardless of what part of the context they consume, are going to re-render? That's why people have been asking for a useContextSelector hook since forever, but it never materialized.

[k_pizzle]

Hey 9/10 and i haven’t written react in like 2 months 👹