Question 1

How do you pass data between components in React?

Accepted Answer

**Target Audience:** Engineers preparing for React interviews — assumes props and state basics. **Difficulty:** Easy to Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. The composition measurement referenced in section 6 was produced by counting real renders on React 19.2.8; see composition for the full figures. ## 1. Why This Ev

Question 2

What is the Context API in React and when would you use it?

Accepted Answer

**Target Audience:** Engineers preparing for React interviews — assumes props and state. **Difficulty:** Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. The default-value and re-render behaviour below were measured on React 19.2.8. This doc covers *what Context is and when to use it*; why it re-renders every consumer covers

Question 3

What is 'prop drilling' and how can it be avoided?

Accepted Answer

**Target Audience:** Engineers preparing for React interviews — assumes props and components. **Difficulty:** Medium > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. The re-render figures quoted in section 4 were measured on React 19.2.8; see avoiding re-renders with composition for the full run. ## 1. Why This Even Matters — A

Question 4

What is `useFormStatus` in React 19, and why does it exist?

Accepted Answer

**Target Audience:** Engineers preparing for React interviews — assumes Actions. **Difficulty:** Hard > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. The measurement in section 3 was **executed against React 19.2.8** by calling the hook in two places at once during a real submission. Its sibling is

Question 5

How do you optimize React component rendering?

Accepted Answer

**Target Audience:** Engineers preparing for senior React interviews — assumes profiling basics. **Difficulty:** Hard > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. The durations in section 3 were measured with React's own Profiler component on React 19.2.8. This doc is about **cost per render**; preventing unnecessary r

Question 6

cache() and fetch memoization — request deduplication in RSC

Accepted Answer

**Target Audience:** Engineers preparing for senior React interviews — assumes Server Components basics. **Difficulty:** Hard > **How to read this doc:** Concepts are explained in plain language first, then tagged with 📌 Interview term:. **A note on verification:** cache()'s deduplication only operates inside a React server render, which cannot be exercised in a unit environment. What *was* verified here is that the API exists and that outside a server render it delib

REACT.JSDECODED.

Easy