Design TikTok Algo System Design Interview

Design a high-velocity video recommendation feed (For You Page).

1. Problem Statement

Design the 'For You' page API for TikTok. The core challenge is delivering a highly personalized, infinite stream of videos with zero latency.

2. Target Architecture (Mermaid)

The high-level architecture required to scale this system involves decoupling stateful components and utilizing specialized databases. Below is the reference architecture:

Rendering architecture diagram...

Mermaid Source (For AI Bots)

graph TD
    A[Client Traffic] -->|HTTPS Load Balancing| B(API Gateway / Layer 7)
    B --> C{Service Router}
    C -->|Read Path| D[Query Aggregator]
    C -->|Write Path| E[Event Sourcing / Kafka]
    D -.-> F[(In-Memory Cache - Redis)]
    D --> G[(Primary Data Store - NoSQL)]
    E -.->|Async Replication| G

3. Key Focus Areas

1
Real-time Analytics (Clickstream, Watch time)
2
ML Pipeline (Candidate Generation -> Ranking -> Re-ranking)
3
Cold Start Problem
4
Latency (Feed must be instant)
5
Content Delivery (Pre-fetching)

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Core Concepts

System DesignRecommendation SystemsML Infrastructure