Rubrik India Backend Engineer Interview: Rounds, Questions and Preparation

What the job involves

Backend engineers in Indian SaaS and B2B product companies build and maintain the server-side systems that power multi-tenant applications, APIs, and data pipelines. They work on scalability, reliability, and performance for enterprise customers, often dealing with large data volumes and strict uptime requirements. Day to day involves writing code, reviewing designs, debugging production issues, and collaborating with frontend, product, and DevOps teams.

Role and technical knowledge

1. 1

   What happens when you type a URL into a browser and press Enter, focusing on the backend aspects?

   Cover DNS resolution, TCP handshake, HTTP request, server-side routing, database queries, and response. Mention caching and load balancers if relevant.

2. 2

   How would you design a multi-tenant database schema for a SaaS product where each customer's data must be isolated?

   Discuss shared schema with tenant ID, separate schemas, or separate databases. Compare trade-offs in cost, isolation, and maintenance.

3. 3

   Explain the difference between SQL and NoSQL databases. When would you choose one over the other for a B2B product?

   Cover consistency, scalability, schema flexibility, and query patterns. Give examples like PostgreSQL vs. MongoDB or Cassandra for specific use cases.

4. 4

   What are the key considerations when designing a REST API for an enterprise SaaS product?

   Mention versioning, authentication (OAuth, API keys), rate limiting, pagination, error handling, and idempotency for safe retries.

Practical scenarios

1. 5

   A customer reports that their API calls are intermittently slow. How would you debug and resolve this?

   Outline steps: check logs and metrics, identify patterns (time of day, endpoint), inspect database queries, look for N+1 issues, check external dependencies, and add caching or indexing.

2. 6

   You need to add a new feature that requires a database migration on a live production system with zero downtime. How do you approach it?

   Discuss backward-compatible migrations, adding columns as nullable, backfilling data, using feature flags, and rolling out in phases.

3. 7

   How would you handle a sudden spike in traffic to your service during a product launch?

   Talk about auto-scaling, load balancing, caching, rate limiting, queueing, and pre-warming. Mention monitoring and alerting.

4. 8

   You discover a bug that causes data inconsistency between two microservices. How do you fix it and prevent recurrence?

   Suggest identifying the root cause, writing a repair script, adding idempotency, using transactions or sagas, and improving integration tests.

Behavioural and HR

1. 9

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

   Use STAR format. Highlight self-learning resources, hands-on practice, and how you applied it to deliver results.

2. 10

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

   Show respect, data-driven discussion, willingness to listen, and focus on the best outcome for the project.

3. 11

   Why do you want to work in a SaaS or B2B product company like ours, rather than a consumer tech company?

   Mention interest in solving complex enterprise problems, working with scalable systems, and the impact on business customers.

4. 12

   Where do you see yourself in three years, and how does this role fit into your career goals?

   Align with growth in backend engineering, deepening system design skills, and taking ownership of critical services.

Coding and problem solving

1. 13

   Given a list of API request logs, write a function to find the top K endpoints by average response time.

   Clarify input format, handle ties, and discuss time complexity. Use a hash map to aggregate and a heap for top K.

2. 14

   Implement a rate limiter that allows N requests per user per minute.

   Discuss sliding window or token bucket. Code a simple in-memory version and mention distributed caching for production.

3. 15

   How would you detect a cycle in a directed graph representing service dependencies?

   Use DFS with recursion stack or Kahn's algorithm. Explain why cycle detection matters for deployment order.

4. 16

   Write a SQL query to find customers who have not placed any orders in the last 30 days.

   Use LEFT JOIN and WHERE with date filter, or NOT EXISTS. Discuss indexing on order date and customer ID.