Bira91 Software Engineer Interview: Rounds, Questions and Preparation

What the job involves

Software Engineers at Indian unicorns and high-growth startups like Bira91 build and maintain customer-facing apps, internal tools, and data pipelines that support rapid scaling. Day to day involves writing clean code, reviewing peers' work, debugging production issues, and shipping features in short agile cycles. You often wear multiple hats, from API design to basic DevOps, in fast-paced environments.

Role and Technical Knowledge

1. 1

   How would you design a database schema for a subscription-based beverage delivery service like Bira91's potential D2C model?

   Discuss entities like users, subscriptions, orders, products, and deliveries. Mention normalization, indexing, and choice of SQL vs NoSQL based on read/write patterns.

2. 2

   Explain how you would implement a rate limiter for an API endpoint that handles order placements during a flash sale.

   Cover token bucket or sliding window algorithms, use of Redis for distributed rate limiting, and how to return 429 status codes gracefully.

3. 3

   What are the key differences between monolithic and microservices architecture? When would you choose one over the other for a fast-growing startup?

   Highlight trade-offs in deployment, scaling, and team autonomy. Suggest starting with a monolith and migrating to microservices as the team and load grow.

4. 4

   How would you optimize a slow SQL query that retrieves the top 10 most ordered products in the last 24 hours?

   Mention adding indexes on order timestamp and product ID, using EXPLAIN to analyze, and possibly caching results in Redis if the query is frequent.

Practical Scenarios

1. 5

   You are asked to add a new feature to an existing codebase, but you have no documentation. How do you proceed?

   Talk about reading tests, tracing code paths, asking teammates, and writing small experiments. Emphasize incremental understanding and not breaking existing functionality.

2. 6

   During a production deployment, you notice a sudden spike in error rates. What steps do you take?

   Suggest rolling back the deployment first, then checking logs and monitoring dashboards. Communicate with the team and conduct a post-mortem to prevent recurrence.

3. 7

   You need to integrate a third-party payment gateway for a new checkout flow. What factors do you consider?

   Cover API reliability, security (PCI compliance), error handling, idempotency, and fallback mechanisms. Mention testing in sandbox and monitoring success rates.

4. 8

   A product manager asks for a feature that you think will take two weeks, but they want it in three days. How do you handle this?

   Explain breaking down the feature into smaller deliverable parts, negotiating scope, and communicating trade-offs clearly. Show willingness to find a minimal viable solution.

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 the STAR method. Focus on your learning strategy, resources used, and the outcome. Highlight adaptability and self-driven learning.

2. 10

   Describe a situation where you disagreed with a teammate's technical decision. How did you resolve it?

   Show respect for others' opinions, data-driven discussion, and willingness to compromise. Emphasize the team's goal over personal ego.

3. 11

   Why do you want to work at a high-growth startup like Bira91 instead of a larger, more established company?

   Mention desire for ownership, fast-paced learning, and impact. Connect to the company's mission and your willingness to wear multiple hats.

4. 12

   How do you prioritize tasks when you have multiple deadlines and limited time?

   Discuss using urgency vs importance matrix, communicating with stakeholders, and focusing on high-impact tasks. Give a concrete example if possible.

Problem Solving and Coding

1. 13

   Given an array of integers representing daily sales, find the maximum profit you can achieve by buying and selling once.

   Explain the single-pass solution tracking minimum price and maximum profit. Mention time complexity O(n) and space O(1).

2. 14

   Write a function to detect if a linked list has a cycle. How would you find the starting node of the cycle?

   Describe Floyd's cycle-finding algorithm (tortoise and hare). For finding start, reset one pointer to head and move both one step until they meet.

3. 15

   How would you find the first non-repeating character in a string? What is the time and space complexity?

   Use a hash map to count frequencies, then iterate to find first with count 1. Time O(n), space O(1) for fixed character set.

4. 16

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

   Use two stacks: one for actual elements, one for minimums. Or store pairs of (value, current min) in a single stack.