Blowhot Full Stack Developer Interview: Rounds, Questions and Preparation

What the job involves

Full Stack Developers at Indian unicorns and high-growth startups build and maintain both client-side and server-side components of web applications. They work across the stack to ship features quickly, often owning everything from database design to API development to responsive UI. In fast-moving environments, they collaborate closely with product, design, and QA to iterate rapidly and scale systems.

Role and technical knowledge

1. 1

   What does a full stack developer do differently at a high-growth startup compared to a larger company?

   Highlight the need to wear multiple hats, move fast, and own features end-to-end with less specialization.

2. 2

   Explain the difference between REST and GraphQL, and when you would choose one over the other.

   Cover over-fetching/under-fetching, flexibility, and use cases like mobile apps vs. simple CRUD services.

3. 3

   How would you design a database schema for a simple e-commerce application?

   Discuss entities like users, products, orders, and relationships, and mention normalization and indexing.

4. 4

   What are some key considerations for optimizing the performance of a web application?

   Mention frontend (lazy loading, code splitting) and backend (caching, database indexing, CDN) optimizations.

Practical scenarios

1. 5

   You are building a feature that requires real-time updates, like a notification system. How would you implement it?

   Discuss WebSockets, polling, or server-sent events, and trade-offs in scalability and complexity.

2. 6

   A user reports that a page is loading slowly. How would you debug and fix the issue?

   Outline steps: check network tab, analyze backend response times, profile frontend rendering, and optimize queries.

3. 7

   You need to integrate a third-party payment gateway into your app. What steps would you take?

   Cover API key management, webhook handling, error scenarios, and security best practices.

4. 8

   How would you handle authentication and authorization in a full stack application?

   Mention JWT, sessions, OAuth, role-based access control, and secure storage of tokens.

Behavioural and HR

1. 9

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

   Use STAR method: describe the situation, the technology, how you learned it, and the outcome.

2. 10

   Describe a situation where you disagreed with a team member on a technical approach. How did you resolve it?

   Show empathy, data-driven discussion, and willingness to compromise for the project's benefit.

3. 11

   Why do you want to work at a fast-growing startup like ours?

   Express enthusiasm for impact, learning, and ownership, and tie it to the company's mission or product.

4. 12

   How do you prioritize tasks when you have multiple deadlines?

   Mention techniques like Eisenhower matrix, communication with stakeholders, and focusing on impact.

Coding and problem solving

1. 13

   Write a function to check if a string is a palindrome, considering only alphanumeric characters.

   Discuss two-pointer approach, handling case and non-alphanumeric characters, and edge cases.

2. 14

   Given an array of integers, find two numbers that sum to a target. How would you optimize it?

   Start with brute force, then use hash map for O(n) time, and explain trade-offs.

3. 15

   Explain how you would reverse a linked list iteratively and recursively.

   Walk through pointer manipulation and base cases, and mention time/space complexity.

4. 16

   How would you find the first non-repeating character in a string?

   Use a hash map to count frequencies, then iterate to find the first with count 1.