Booking.com India Software Engineer Interview: Rounds, Questions and Preparation

What the job involves

Software Engineers at global tech product companies build, test, and maintain scalable web or mobile applications that serve millions of users. Day to day involves writing clean code, participating in code reviews, debugging production issues, and collaborating with product, design, and data teams. Freshers typically start with well-defined features and gradually own larger components.

Role and Technical Knowledge

1. 1

   Explain the difference between a process and a thread. How does this impact a web server handling multiple requests?

   Cover memory isolation, context switching, and how multithreading or multiprocessing helps scale request handling.

2. 2

   What are ACID properties in a database? Give an example of a transaction that must satisfy them.

   Define Atomicity, Consistency, Isolation, Durability and use a money transfer between two accounts as a classic example.

3. 3

   How does a REST API differ from a SOAP API? When would you choose one over the other?

   Highlight statelessness, payload formats (JSON vs XML), and use cases like public APIs vs enterprise legacy systems.

4. 4

   What is the time complexity of common operations on a hash table? How would you handle collisions?

   Discuss average O(1) for insert, delete, search, and collision resolution techniques like chaining or open addressing.

Practical Scenarios

1. 5

   You are asked to design a URL shortener like bit.ly. What components would you include and how would you ensure it scales?

   Mention a database for mappings, a hashing or encoding service, caching for hot URLs, and load balancing for scale.

2. 6

   A feature you deployed is causing a memory leak in production. How would you debug and fix it?

   Describe using profiling tools, analysing heap dumps, checking for unclosed resources, and rolling back if needed.

3. 7

   How would you test a function that calculates the total price of a shopping cart with discounts and taxes?

   Outline unit tests for edge cases like empty cart, multiple discounts, tax rounding, and invalid inputs.

4. 8

   You need to fetch data from a third-party API that is slow and sometimes fails. How would you make your application resilient?

   Suggest caching, retries with exponential backoff, circuit breakers, and fallback responses.

Behavioural and HR

1. 9

   Tell me about a time you had to learn a new technology quickly for a project. How did you approach it?

   Use STAR method: describe the situation, your learning strategy, the outcome, and what you would do differently.

2. 10

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

   Focus on active listening, data-driven discussion, and reaching a consensus without personal conflict.

3. 11

   Why do you want to work at a global tech company like Booking.com India?

   Connect your interest to the company's scale, products, engineering culture, and your long-term growth goals.

4. 12

   Where do you see yourself in three years?

   Show ambition to deepen technical expertise, take ownership of modules, and contribute to team success.

Coding and Problem Solving

1. 13

   Given an array of integers, find two numbers that add up to a target sum. Return their indices.

   Explain brute force O(n^2) then optimise to O(n) using a hash map, and discuss edge cases like duplicates.

2. 14

   Reverse a linked list iteratively and recursively. What are the time and space complexities?

   Walk through pointer manipulation, mention O(n) time for both, and O(1) vs O(n) space for iterative vs recursive.

3. 15

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

   Use a hash map to count frequencies in one pass, then iterate to find the first with count 1, O(n) time.

4. 16

   Implement a stack that supports push, pop, and retrieving the minimum element in O(1) time.

   Use an auxiliary stack to track minimums, explaining how it updates on push and pop.