Vidyard India Backend Engineer Interview: Rounds, Questions and Preparation

What the job involves

Backend engineers at Indian SaaS and B2B product companies build and maintain the server-side systems that power multi-tenant web applications. Day to day, they write APIs, design database schemas, integrate third-party services, and ensure the product scales reliably for business customers. They work closely with frontend, product, and DevOps teams to ship features that solve real customer problems.

Role and Technical Knowledge

1. 1

   What is multi-tenancy in a SaaS product, and how would you design a database to support it?

   Explain shared vs isolated schemas, tenant ID columns, and trade-offs around cost, security, and query complexity. Mention row-level security or separate databases for large customers.

2. 2

   How would you design a REST API for a video hosting platform that lets users upload, list, and delete videos?

   Cover resource naming, HTTP methods, status codes, pagination, and authentication. Mention handling large file uploads with presigned URLs or chunked uploads.

3. 3

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

   Discuss structured vs flexible schemas, ACID vs eventual consistency, and scaling patterns. Give examples like PostgreSQL for billing data and MongoDB for activity logs.

4. 4

   What happens when a user logs in to a SaaS application? Walk through the backend flow.

   Describe credential validation, password hashing, session or JWT token generation, and storing refresh tokens. Mention rate limiting and secure cookie flags.

Practical Scenarios

1. 5

   A customer reports that their video uploads are failing intermittently. How would you debug this?

   Start with logs, error rates, and recent deployments. Check timeouts, storage limits, and network issues. Suggest adding retries and better error messages.

2. 6

   You need to add a new feature that sends email notifications when a video is commented on. How would you implement it without slowing down the main API?

   Propose a message queue or background job system. Explain decoupling, retries, and idempotency. Mention using a service like SendGrid or SES.

3. 7

   Your API response times are increasing as more customers sign up. What steps would you take to improve performance?

   Suggest database indexing, query optimization, caching with Redis, and horizontal scaling. Mention profiling and monitoring tools.

4. 8

   How would you handle a situation where a third-party API your product depends on goes down?

   Talk about circuit breakers, fallbacks, graceful degradation, and alerting. Emphasize keeping the core product usable and communicating with customers.

Behavioural and HR

1. 9

   Tell me about a time you worked in a team to build something. What was your role and how did you handle disagreements?

   Use the STAR method. Highlight listening, compromising, and focusing on the team goal. Show you can give and receive feedback.

2. 10

   Why do you want to work at a fast-growing SaaS company like Vidyard India instead of a large service-based IT firm?

   Show interest in product ownership, direct customer impact, and learning across the stack. Mention the pace and ownership culture of SaaS startups.

3. 11

   Describe a time you had to learn a new technology quickly for a project or hackathon.

   Explain your learning process, resources used, and how you applied it. Emphasize curiosity and ability to deliver under time constraints.

4. 12

   Where do you see yourself in three years, and how does this backend engineer role fit into that?

   Align your growth with the company's needs, such as becoming a strong backend developer or moving into system design. Show commitment to learning and contributing.

Problem Solving and Coding

1. 13

   Given a list of video view events, write a function to return the top 10 most viewed videos in the last 24 hours.

   Clarify data format and scale. Use a hash map to count views, then a heap or sort for top K. Discuss time and space complexity.

2. 14

   How would you find and fix a bug where duplicate charges are being created for the same subscription?

   Talk about idempotency keys, database transactions, and unique constraints. Suggest logging and monitoring to catch duplicates early.

3. 15

   Write a function to validate an email address and a password according to typical SaaS rules.

   Use regex for email, and check password length, complexity, and common patterns. Mention server-side validation and hashing before storage.

4. 16

   Explain how you would design a rate limiter for an API endpoint that allows 100 requests per minute per user.

   Describe token bucket or sliding window algorithms. Mention using Redis for distributed rate limiting and returning 429 status codes.