Design a Scalable Likes System
Company: Roblox
Role: Software Engineer
Category: System Design
Difficulty: medium
Interview Round: Technical Screen
Design a scalable likes service for a large consumer application. Users can like and unlike an item.
The system must support these functional requirements:
1. Like an item.
2. Unlike an item.
3. Check whether a specific user has liked a specific item.
4. Return the list of items liked by a user, with pagination.
5. Return the total number of likes for an item.
Discuss the API design, data schema, indexing strategy, and how the system should scale to high read and write traffic. Also explain how you would handle duplicate requests, consistency of like counts, and hot items with very large numbers of likes.
Quick Answer: This question evaluates system design and distributed-systems skills, specifically scalability, consistency, API and data schema design, indexing strategies, and handling high read/write traffic for user-action services.