EpiFi Technologies Full Stack Developer Interview: Rounds, Questions and Preparation

What the job involves

As a Full Stack Developer at Indian unicorns and high-growth startups like EpiFi Technologies, you will build and maintain both client-side and server-side components of web applications, often working across the entire stack from UI to database. Expect to ship features rapidly, collaborate with product and design teams, and handle scalability challenges typical of fast-growing fintech and consumer tech companies. The role demands strong fundamentals in JavaScript/TypeScript, a modern frontend framework (React or Vue), backend frameworks (Node.js, Python, or Go), and cloud-native databases.

Role and Technical Knowledge

1. 1

   Explain the difference between client-side and server-side rendering. When would you choose one over the other for a fintech dashboard?

   A strong answer covers SEO, initial load performance, and user experience. For a fintech dashboard, client-side rendering with authenticated APIs is common, but server-side rendering can help with initial data fetch and security.

2. 2

   How would you design a REST API for a user profile system that supports creation, retrieval, update, and deletion?

   Mention proper HTTP methods (POST, GET, PUT/PATCH, DELETE), status codes, and resource naming. Also discuss authentication and validation.

3. 3

   What is the difference between SQL and NoSQL databases? Give an example of when you would use each in a startup like EpiFi Technologies.

   SQL for transactional data with relationships, NoSQL for flexible schemas and high write throughput. For example, user accounts in PostgreSQL and activity logs in MongoDB.

4. 4

   Explain how you would handle authentication and authorization in a full stack application.

   Cover JWT or session-based auth, role-based access control, and secure storage of tokens. Mention HTTPS and password hashing.

Practical Scenarios

1. 5

   You are building a feature that shows real-time transaction updates on a dashboard. How would you implement it?

   Discuss WebSockets or Server-Sent Events, and fallback to polling. Mention state management on the frontend and efficient backend push.

2. 6

   Your web app is slow on mobile devices. What steps would you take to improve performance?

   Cover code splitting, lazy loading, image optimization, caching, and reducing bundle size. Mention measuring with Lighthouse.

3. 7

   You need to integrate a third-party payment gateway. What are the key considerations?

   Security (PCI compliance), error handling, idempotency, and webhook handling. Also mention testing in sandbox mode.

4. 8

   How would you debug a bug that only appears in production but not in your local environment?

   Talk about logging, monitoring tools, reproducing with production-like data, and checking environment differences.

Behavioural and HR

1. 9

   Tell me about a time you had to learn a new technology quickly for a project.

   Use STAR method. Highlight resourcefulness, time management, and the outcome.

2. 10

   Describe a situation where you disagreed with a teammate. How did you handle it?

   Show empathy, communication, and focus on the best solution. Avoid blaming others.

3. 11

   Why do you want to work at a high-growth startup like EpiFi Technologies instead of a large MNC?

   Express interest in ownership, fast-paced learning, and impact. Relate to your career goals.

4. 12

   Where do you see yourself in three years as a full stack developer?

   Show ambition to grow into a senior role, deepen technical expertise, and possibly mentor others.

Problem Solving and Coding

1. 13

   Given an array of integers, find two numbers that add up to a target sum. Write the function and explain its time complexity.

   Use a hash map for O(n) time. Explain the trade-off with sorting and two-pointer approach.

2. 14

   How would you implement a function to debounce user input in JavaScript?

   Explain closures, setTimeout, and clearTimeout. Show a simple implementation and use case.

3. 15

   Write a SQL query to find the second highest salary from an Employee table.

   Use subquery with LIMIT/OFFSET or window function. Discuss handling ties and nulls.

4. 16

   Design a URL shortener like bit.ly. What are the key components and how would you scale it?

   Cover hashing, database choice, caching, and load balancing. Mention base62 encoding.