React Interview Topics for 9+ Years Java Full Stack Developers

This guide organizes the React topics that are most valuable for experienced Java Full Stack developers (9+ years). The emphasis is on architecture, performance, integration with Spring Boot, and senior-level interview expectations.

High-Priority Topics (Must Know)

These topics are commonly asked in senior Java Full Stack interviews.

Topic	Interview Frequency	Expected Depth
React Lifecycle using Hooks	*****	Senior
useState	*****	Senior
useEffect	*****	Senior
useMemo	*****	Senior
useCallback	*****	Senior
useRef	****	Senior
React.memo	****	Senior
Context API	*****	Senior
Redux Basics	****	Senior
Routing	*****	Senior
JWT Authentication	*****	Senior
Axios Interceptors	*****	Senior
React + Spring Boot Integration	*****	Senior

Architecture Topics

Senior interviewers frequently focus on architecture and application design.

Topics include:

Component Design
React Project Architecture
Performance Optimization
Code Splitting
Lazy Loading
Virtual DOM
Reconciliation

You should understand:

Why React components re-render
How React compares Virtual DOM trees
Memoization strategies
Bundle optimization
Feature-based folder structure
API layer organization
Authentication flow
Error Boundaries

High-Level React Architecture

flowchart LR
    UI[React Components]
    Router[React Router]
    State[Context API / Redux]
    API[Axios Service Layer]
    Auth[JWT Authentication]
    Backend[Spring Boot REST APIs]
    DB[(Database)]

    UI --> Router
    UI --> State
    UI --> API
    API --> Auth
    API --> Backend
    Backend --> DB

Moderate-Priority Topics

These are common follow-up questions.

Custom Hooks
Controlled vs Uncontrolled Components
Forms
Error Handling
Debouncing
Throttling
Infinite Scroll
Pagination
React Query / TanStack Query
Optimistic Updates

React + Spring Boot Integration

For Java Full Stack roles, this is one of the highest-value interview areas.

Typical questions include:

How does React communicate with Spring Boot?
Why use Axios?
How do you send JWT tokens?
How do you refresh expired tokens?
How do CORS issues occur?
Difference between Session Authentication and JWT
File upload
File download
Handling HTTP 401 responses globally
API security

See the React + Spring Boot Integration Interview Guide for a full walkthrough of architecture, CORS, JWT auth, file upload/download, pagination, and deployment strategies.

Typical Request Flow

sequenceDiagram
    participant User
    participant React
    participant Axios
    participant SpringBoot
    participant Database

    User->>React: Perform action
    React->>Axios: REST API request
    Axios->>SpringBoot: HTTP request + JWT
    SpringBoot->>Database: Query/Update
    Database-->>SpringBoot: Result
    SpringBoot-->>Axios: JSON response
    Axios-->>React: Process response
    React-->>User: Update UI

Performance Questions

Senior candidates are expected to answer questions such as:

Why is my component rendering multiple times?
How do you optimize React applications?
Explain useMemo.
Explain useCallback.
Difference between useMemo and React.memo.
Difference between useRef and useState.
How do you optimize a large table?
What is virtualization?
What is lazy loading?
What are dynamic imports?
What is code splitting?

Common Coding Exercises

Typical interview implementations include:

Todo CRUD
Search filter
Debounced search
Pagination
Infinite scroll
Dynamic forms
File upload
Image preview
Authentication flow
Login page
Dashboard
Modal
Tabs
Accordion

Senior Scenario-Based Questions

Examples:

Why is useEffect executing twice?
Parent updates but child should not re-render. How do you prevent it?
A page displays 1000 rows and performs poorly. How do you optimize it?
An API is being called multiple times unexpectedly. How do you debug and fix it?
JWT expires after 30 minutes. How would you refresh it?
How do you synchronize logout across multiple browser tabs?
How would you structure a React application with 100+ components?
How would you implement role-based access control (RBAC)?
How do you protect routes?
How do you avoid prop drilling?

Advanced Topics

These topics help distinguish senior candidates.

Context API vs Redux
Redux Toolkit
Redux Middleware
Redux Thunk vs Redux Saga
Render Props
Higher Order Components (HOCs)
Custom Hooks
Error Boundaries
Suspense
Concurrent Rendering
Strict Mode
Hydration
Server-Side Rendering (SSR)
Client-Side Rendering (CSR)
Static Site Generation (SSG)

Topics Already Covered

The following interview areas are already covered on this site:

Context API - see React Context API Interview Guide
React + Spring Boot Integration - see React + Spring Boot Integration Interview Guide

Key Takeaways

Senior Java Full Stack interviews emphasize architecture, performance, and integration more than basic React syntax.
React + Spring Boot integration, JWT authentication, routing, Axios, and state management are core expectations.
Performance optimization and rendering behavior are frequent discussion topics.
Scenario-based questions are common for experienced candidates.
Completing the recommended additional topics provides excellent coverage for most product and service company interviews.