Dailyhunt Backend Engineer Interview: Rounds, Questions and Preparation

What the job involves

Backend engineers at Indian unicorns and high-growth startups like Dailyhunt build and maintain the server-side systems that power content delivery, user personalisation, and real-time analytics. Day to day, they write APIs, optimise database queries, handle large-scale data pipelines, and ensure low-latency responses for millions of users. They work closely with product, data, and mobile teams to ship features quickly in a fast-paced environment.

Role and technical knowledge

1. 1

   How would you design a URL shortener that handles millions of requests per day?

   Cover hashing or base62 encoding, database choice (SQL vs NoSQL), caching with Redis, and handling collisions.

2. 2

   Explain the difference between SQL and NoSQL databases. When would you choose one over the other for a content feed like Dailyhunt's?

   Discuss schema flexibility, scaling (vertical vs horizontal), consistency models, and use cases like user profiles vs article metadata.

3. 3

   What is a REST API? How do you ensure it is secure and efficient?

   Mention HTTP methods, status codes, authentication (JWT/OAuth), rate limiting, and pagination for large datasets.

4. 4

   How does caching work in a backend system? What are common eviction policies?

   Explain LRU, LFU, TTL, and where to place caches (client, CDN, application, database) for read-heavy workloads.

Practical scenarios

1. 5

   You notice that an API endpoint is responding slowly during peak hours. How would you debug and fix it?

   Outline steps: check logs, profile database queries, add indexes, introduce caching, and consider horizontal scaling.

2. 6

   How would you handle a sudden spike in traffic to a news article that goes viral?

   Discuss auto-scaling, load balancers, CDN for static assets, read replicas, and queueing non-critical tasks.

3. 7

   You need to implement a feature that sends personalised push notifications to millions of users. What is your approach?

   Cover message queues (Kafka), batch processing, user segmentation, and avoiding synchronous blocking calls.

4. 8

   How would you ensure data consistency between a primary database and a cache?

   Explain write-through, write-behind, cache invalidation strategies, and handling race conditions with versioning.

Behavioural and HR

1. 9

   Tell me about a time you worked on a team project and faced a conflict. How did you resolve it?

   Use STAR method: describe situation, task, action (communication, compromise), and positive outcome.

2. 10

   Why do you want to work at a high-growth startup like Dailyhunt rather than a large MNC?

   Show enthusiasm for fast-paced learning, ownership, and impact. Mention specific products or technologies the company uses.

3. 11

   Describe a situation where you had to learn a new technology quickly to complete a task.

   Highlight self-learning, resourcefulness, and applying the new skill to deliver results under a deadline.

4. 12

   Where do you see yourself in the next three years?

   Align your growth with the company's needs: becoming a strong backend engineer, mentoring juniors, and contributing to scalable systems.

Coding and problem solving

1. 13

   Given a list of integers, find the longest increasing subsequence. Write code and explain time complexity.

   Use dynamic programming O(n^2) or binary search O(n log n). Discuss edge cases like empty array.

2. 14

   How would you detect a cycle in a linked list? Implement it.

   Use Floyd's cycle detection (tortoise and hare). Explain why it works and its O(n) time, O(1) space.

3. 15

   Design a data structure that supports insert, delete, and getRandom in O(1) time.

   Combine an array and a hash map. Explain how to swap with the last element for deletion.

4. 16

   Write a function to check if a binary tree is a valid binary search tree.

   Use in-order traversal or recursive range checking. Discuss handling duplicate values and null nodes.