What TikTok system design interview questions to expect?

Example Question:

"Design a system for streaming short-form videos like TikTok. How would you ensure high availability and low latency for millions of users worldwide?"

2. Design a Real-Time Recommendation System (For You Page)

TikTok’s recommendation engine is a core feature, and you may be asked to design a system that delivers personalized content to users in real-time.

Key Areas to Focus On:

• Recommendation Algorithms: How would you design the recommendation logic to show relevant content?
• Data Pipeline: Handling user interactions in real-time to update recommendations.
• Scalability: Processing billions of interactions daily while maintaining low latency.
• User Data Processing: Real-time analysis of likes, shares, watch duration, and comments to inform recommendations.

Example Question:

"Design the recommendation engine for TikTok’s For You page. How would you process user interactions and deliver personalized content in real-time?"

3. Design a Real-Time Chat System (for Live Streaming)

TikTok allows users to interact with content creators in real-time during live streams, so you may be asked to design a real-time chat system integrated with live video.

Key Areas to Focus On:

• Message Delivery: How will you ensure real-time message delivery with minimal latency?
• Concurrency: Scaling the system to handle millions of users interacting during a live stream.
• Data Storage: Storing chat histories and user interactions for future reference.
• Moderation: Real-time content moderation to filter inappropriate messages.

Example Question:

"Design a real-time chat system for live video streaming. How would you ensure scalability and real-time delivery of messages to millions of users?"

4. Design a Notification System for TikTok

Another common question involves designing a notification system that sends real-time alerts (push notifications, emails, etc.) to millions of users.

Key Areas to Focus On:

• Scalability: Ensuring the system can handle millions of notifications sent at the same time.
• Reliability: Guaranteeing notifications are delivered reliably even in case of server failures.
• Delivery Channels: Managing multiple delivery channels (push notifications, emails, SMS).
• Prioritization: Handling different priorities for notifications (e.g., critical updates vs. regular notifications).

Example Question:

"Design a notification system for TikTok that sends real-time push notifications and emails to millions of users. How would you ensure scalability and reliability?"

5. Design a Social Media Feed

TikTok has a personalized feed (For You) and a following feed. You could be asked to design a system that delivers a personalized feed with real-time updates.

Key Areas to Focus On:

• Feed Generation: How would you generate a personalized feed based on user preferences and interactions?
• Real-Time Updates: Ensuring that users’ feeds are updated in real-time as new content is posted.
• Caching: Using caching to improve performance and reduce load on backend systems.
• Data Consistency: Handling data consistency issues when showing real-time updates.

Example Question:

"Design a social media feed for TikTok. How would you handle real-time updates, data consistency, and scalability for millions of users?"

6. Design a Content Moderation System

Given TikTok’s vast user-generated content, content moderation is critical. You might be asked to design a system that can automatically detect and remove inappropriate content.

Key Areas to Focus On:

• Automated Detection: How would you use AI/ML models to automatically detect harmful or inappropriate content (e.g., violence, hate speech)?
• Scalability: Handling moderation for millions of pieces of content uploaded every day.
• Human Review: When and how would you integrate human reviewers into the process?
• False Positives and Accuracy: Minimizing false positives while ensuring harmful content is removed quickly.

Example Question:

"Design a content moderation system for TikTok. How would you scale the system to detect and filter inappropriate content in real-time?"

7. Design a Distributed File Storage System

Another possible design question could involve building a distributed file storage system, which is critical for storing large volumes of video content in a reliable and scalable way.

Key Areas to Focus On:

• Data Replication and Consistency: How will you ensure data is replicated across different regions to ensure availability and fault tolerance?
• Fault Tolerance: How will the system recover from server failures while ensuring data isn’t lost?
• Sharding and Partitioning: How will you split large files across multiple servers for efficiency and speed?
• Data Retrieval: Ensuring fast retrieval of video files across different geographical regions.

Example Question:

"Design a distributed file storage system for TikTok. How would you ensure scalability, fault tolerance, and fast access to video files?"

8. Design a CDN for Video Delivery

A content delivery network (CDN) is crucial for delivering video content quickly to TikTok users worldwide. You may be asked to design a system for caching and delivering videos efficiently.

Key Areas to Focus On:

• Caching: How would you cache video content at edge locations to reduce latency?
• Load Balancing: How would you distribute traffic across CDN nodes to prevent overload?
• Scalability: Handling global traffic while ensuring low latency in different regions.
• Fault Tolerance: Ensuring continuous video delivery even if one CDN node goes down.

Example Question:

"Design a CDN for video delivery for TikTok. How would you handle traffic spikes, ensure low latency, and maintain fault tolerance?"

How to Approach TikTok System Design Questions

1. Ask Clarifying Questions

Start by asking questions to understand the exact requirements, such as:

• Target user base (millions, billions of users?).
• Expected read/write throughput.
• Latency requirements.

2. Break the System Into Components

After clarifying the requirements, break the system down into key components such as:

• Front-end and back-end services.
• Databases and data storage.
• Caching, CDNs, and load balancers.
• Real-time processing and batch jobs.

3. Discuss Scalability and Fault Tolerance

Make sure to explain how your system will scale to handle millions of users while remaining fault-tolerant in case of failures.

4. Consider Trade-offs

Discuss trade-offs between performance, scalability, and consistency. For example, explain why you might prioritize low latency over data consistency in a video streaming system.

Preparation Resources

Recommended Courses:

• Grokking System Design Fundamentals: This course helps you understand the basics of scalable system design.
• Grokking the System Design Interview: Perfect for practicing real-world system design scenarios.

Mock Interviews:

• System Design Mock Interview: Practice mock system design interviews to improve your approach and communication.

Final Thoughts

In TikTok's system design interview, you can expect questions that focus on building large-scale, real-time systems. Be prepared to discuss scalability, fault tolerance, performance optimization, and real-time data processing. Practicing with structured resources and mock interviews will help you succeed in these complex design challenges.