Design Instagram Feed System Design Interview

Design a photo-sharing social network news feed with complex ranking.

1. Problem Statement

Design the news feed for Instagram. Users follow people and see a ranked list of photos/videos. Focus on the backend architecture.

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
Feed Generation (Push vs Pull / Fan-out)
2
Ranking Algorithms (EdgeRank, Machine Learning signals)
3
Data Model (User, Media, Follows)
4
Caching (User Sessions, CDN for images)
5
Pagination (Cursor-based)

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Core Concepts

System DesignSocial NetworksScalability