React Native Interview Handbook — Part 5 of 10: Senior & System Design

#reactnative #javascript #react #career

This guide is part of a 719-question React Native interview handbook collected from real interviews across startups, product companies, fintech, e-commerce, and MNCs. Questions range from beginner to senior (5+ years) and cover JavaScript, React Native, New Architecture, performance, security, native modules, iOS, Android, system design, and behavioral interviews.

This article contains 159 questions (global questions 561–719). Answer each question before reading the response, explain assumptions and complexity for coding questions, and adapt behavioral examples to your truthful experience.

Difficulty guide

🟢 Beginner — expected for entry-level and junior React Native roles.
🟡 Intermediate — expected for engineers who can independently ship features.
🔴 Senior — tests architecture, trade-offs, production ownership, and native-platform knowledge.

Topics in this part

Coding Problems — questions 48–75
Output-Based JavaScript Questions — 111 questions
Scenario-Based Questions — 13 questions
HR & Behavioral Questions — 7 questions

Complete series

This Dev.to series has five core handbook articles plus five focused practice extras. Open the series page to move through the complete reading order:

Part 1: JavaScript — core handbook, questions 1–120
Part 2: React — core handbook, questions 121–220
Part 3: React Native — core handbook, questions 221–420
Part 4: Performance & Architecture — core handbook, questions 421–560
Part 5: Senior & System Design — core handbook, questions 561–719
Part 6: Output-Based JavaScript Practice — bonus practice article
Part 7: Coding Interview Practice — bonus practice article
Part 8: Code Output Challenges — bonus practice article
Part 9: Current React Native Interview Questions — new high-frequency practice article
Part 10: Project & Production Interviews — senior project ownership and real-production practice

Series navigation

Use the Complete React Native Interview Handbook 2026 series page on Dev.to to open every part in order.

Continuation note

Code example:

const source = { missing: undefined, createdAt: new Date() };
const clone = JSON.parse(JSON.stringify(source));
console.log(clone); // createdAt is a string; missing is removed

class LRUCache {
  constructor(capacity) {
    this.capacity = capacity;
    this.cache = new Map();
  }

  get(key) {
    if (!this.cache.has(key)) return undefined;
    const value = this.cache.get(key);
    this.cache.delete(key);
    this.cache.set(key, value);
    return value;
  }

  set(key, value) {
    this.cache.delete(key);
    this.cache.set(key, value);
    if (this.cache.size > this.capacity) {
      this.cache.delete(this.cache.keys().next().value);
    }
  }
}

Output-Based JavaScript Questions

Code example:

for (var i = 0; i < 3; i++) setTimeout(() => console.log(i)); // 3 3 3
for (let i = 0; i < 3; i++) setTimeout(() => console.log(i)); // 0 1 2

6. onEndReached fires multiple times and duplicates pagination data. How do you fix it?

Answer

❌ “useMemo always improves performance.”

✅ Memoization adds comparison, allocation, and maintenance costs. Profile first.
❌ “React Native uses the DOM.”

✅ React Native uses React reconciliation with native host views, not browser DOM nodes.
❌ “AsyncStorage is safe for tokens.”

✅ Store credentials in Keychain/Keystore-backed secure storage; keep server secrets off-device.
❌ “Promise.all cancels remaining requests after one rejection.”

✅ It rejects early, but other operations may continue unless explicitly cancelled.
❌ “The New Architecture makes every app fast.”

✅ It reduces important boundary costs; slow renders, large images, and blocking work still need profiling.

Company and role preparation

Company-specific interview questions vary by team and change over time. Use these as preparation lenses, not claims about a company's fixed interview process.

Microsoft — cross-platform architecture, TypeScript, accessibility, testing, and collaboration.
PhonePe, Razorpay, Zeta, and CRED — payments, secure authentication, idempotency, offline recovery, and incident response.
Swiggy — high-volume feeds, location, notifications, performance, and unreliable networks.
Amazon and Walmart — scalable UI, operational excellence, customer impact, ownership, and system design.
Deloitte and consulting roles — client communication, delivery, debugging across environments, and explaining trade-offs clearly.

Downloadable preparation checklist

Copy this into your notes and mark each subject only after you can explain it, implement a small example, and answer at least two follow-up questions.