React Native Interview Question

🚀 Cracking React Native Interviews – My Developer’s Perspective

Over the years of building real-world React Native apps, I’ve realized that interviews don’t just test syntax — they test how you think as an engineer. Here’s my take on some of the most commonly asked questions 👇

1️⃣ What is React Native and why is it efficient for cross-platform apps? ⚙️

React Native lets us build iOS and Android apps using JavaScript & React while rendering real native UI components.

Instead of writing Swift + Kotlin separately, we write one codebase that runs everywhere. This reduces:

• Development time
• Team size
• Bugs across platforms

Yet performance stays close to native because React Native talks directly to native APIs. 🚀

2️⃣ How does React Native work internally? (Bridge vs New Architecture) 🏗️

Old Architecture (Bridge) JS and Native talk via a bridge by sending JSON messages. This was async but could become a bottleneck.

New Architecture (Fabric + TurboModules) Now React Native uses:

• JSI (JavaScript Interface)
• Direct calls between JS & Native

No JSON, no bridge bottleneck → faster, more synchronous & more memory-efficient apps.

3️⃣ Most challenging task I handled 🛠️

One of the hardest problems I solved was secure API communication:

• AES + RSA encryption
• SSL pinning
• Encrypted request/response flow
• Integrated with RTK Query

Getting this right across Android & iOS while keeping performance stable was a true engineering challenge.

4️⃣ Is JavaScript tightly coupled or loosely coupled? 🔗

JavaScript is loosely coupled.

Objects interact through:

• Events
• Callbacks
• Promises
• Interfaces

This allows high flexibility, easier refactoring, and better scalability in large apps.

5️⃣ Why do we use TypeScript in mobile apps? 💙

TypeScript gives:

• Compile-time error checking
• Safer refactoring
• Better IDE support
• Predictable APIs

In large React Native projects, TypeScript prevents runtime crashes before they happen.

6️⃣ extends, type vs interface 📝

extends lets one type or interface inherit another.

Example: User → Admin → SuperAdmin

interface

• Best for objects & classes
• Supports declaration merging

type

• Better for unions, intersections, primitives

In real projects, I use:

• interface for APIs & props
• type for complex logic types

7️⃣ How Redux works 📦

Redux is about: Store → Actions → Reducers → UI

Flow:

1. UI dispatches an action
2. Reducer updates state
3. Store notifies components
4. UI re-renders

With Redux Toolkit:

• No boilerplate
• Built-in immutability
• Built-in async logic (RTK Query)

8️⃣ RTK or TanStack Query? ⚡

Yes — I’ve used both.

• RTK Query → Best when using Redux already
• TanStack Query → Best for server-state, caching, retries, background refetch

Both solve:

• Loading states
• Error handling
• API caching
• Data synchronization

9️⃣ bind vs apply 🛠️

Both set the value of this.

• bind() → returns a new function
• apply() → immediately calls the function with arguments array

bind is for later execution, apply is for immediate execution.

🔟 useCallback & useMemo in real projects 🏎️

These hooks prevent unnecessary re-renders.

I use them when:

• Passing functions to child components
• Running expensive calculations
• Optimizing FlatLists & heavy UI

They improve performance, especially in large mobile screens.

1️⃣1️⃣ Role of dependency array in useEffect 🔄

The dependency array controls when useEffect runs.

• Empty [] → run once
• [x] → run when x changes
• No array → run on every render

Wrong dependencies = bugs, infinite loops, stale data 😅

✨ Final Thought

React Native is not just a framework — it’s an ecosystem of architecture, performance, state management, and type safety.

The better you understand the “why” behind the tools, the better engineer you become. 💪

If this helped you, feel free to share or drop a comment 🚀