IDfy Software Engineer Interview: Rounds, Questions and Preparation

What the job involves

As a Software Engineer at an Indian SaaS or B2B product company, you will build and maintain features for cloud-based platforms used by businesses for tasks like identity verification, payments, or workflow automation. Day to day, you will write clean code, debug issues, collaborate with product and QA teams, and ensure your services are reliable and scalable. You will also participate in code reviews and gradually take ownership of small modules.

Role and Technical Knowledge

1. 1

   What is a REST API and how would you design one for a service that verifies user documents?

   Explain REST principles like statelessness and HTTP methods. For document verification, mention endpoints for upload, status check, and result retrieval, with proper authentication and error handling.

2. 2

   Explain the difference between SQL and NoSQL databases. Which would you choose for storing user KYC data and why?

   Compare schema flexibility, scalability, and consistency. For KYC data, SQL is often preferred due to structured data and ACID compliance, but mention trade-offs based on access patterns.

3. 3

   How does Git work and what is your typical workflow when collaborating on a feature?

   Describe branching, commits, pull requests, and code reviews. Emphasize clear commit messages and resolving merge conflicts.

4. 4

   What are some key considerations for building a multi-tenant SaaS application?

   Discuss data isolation, tenant-specific configurations, scalability, and security. Mention approaches like shared database with tenant ID or separate schemas.

Practical Scenarios

1. 5

   You are asked to reduce the response time of an API that fetches user verification status. How would you approach this?

   Start by profiling to find bottlenecks. Suggest caching, database indexing, query optimization, or asynchronous processing. Mention measuring impact with metrics.

2. 6

   A bug is reported where some users see incorrect verification results. How do you debug and fix it?

   Reproduce the issue, check logs, and trace data flow. Consider edge cases like race conditions or stale cache. Propose a fix and add tests to prevent regression.

3. 7

   You need to integrate a third-party API for address verification. What steps would you take?

   Cover reading API docs, handling authentication, error cases, rate limits, and data mapping. Mention writing a wrapper and adding retries with backoff.

4. 8

   How would you ensure your code is testable and maintainable in a fast-paced SaaS environment?

   Talk about unit tests, mocking dependencies, modular design, and code reviews. Emphasize writing clear, documented code and using CI/CD pipelines.

Behavioural and HR

1. 9

   Why do you want to work in the Indian SaaS and B2B product sector, and what excites you about companies like IDfy?

   Show awareness of the sector's growth and impact on businesses. Mention interest in solving real-world problems at scale and learning from product-focused engineering.

2. 10

   Describe a time you worked in a team to complete a project. What was your role and how did you handle disagreements?

   Use STAR method. Highlight collaboration, communication, and willingness to compromise. Focus on the outcome and what you learned.

3. 11

   Tell me about a technical challenge you faced and how you overcame it.

   Pick a specific example, explain the problem, your approach, and the result. Show persistence, learning, and resourcefulness.

4. 12

   Where do you see yourself in three years, and how does this role align with your goals?

   Express a desire to grow technically and take on more ownership. Align with the company's focus on product development and customer impact.

Problem Solving and Algorithms

1. 13

   Given a list of user IDs, find the first duplicate ID. How would you optimize for time and space?

   Discuss using a hash set for O(n) time and O(n) space. Mention trade-offs if memory is constrained, like sorting first.

2. 14

   How would you design a function to validate an Indian phone number? Consider different formats.

   Outline regex patterns, handling country codes, and edge cases like landlines. Mention writing tests for various inputs.

3. 15

   Explain how you would implement a rate limiter for an API endpoint.

   Cover algorithms like token bucket or sliding window. Discuss where to store counters (in-memory vs. Redis) and how to return 429 status codes.

4. 16

   What is the time complexity of your solution, and how would you improve it if the input size grows significantly?

   Be precise about Big O notation. Suggest optimizations like using better data structures, caching, or parallel processing if applicable.