Design an Ad Click Aggregator System Design Interview

Design a system to track ad clicks and aggregation for real-time analytics and billing.

1. Problem Statement

We serve ads on Facebook/Google. We need to count how many times each ad was clicked in real-time for the dashboard, AND ensure billing is accurate at end of day. How do we do it?

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 aggregation (Count Clicks per Ad)
2
Correctness (Advertisers must be billed correctly)
3
Handling duplicate clicks (Fraud/Network issues)
4
Star Schema vs NoSQL for analytics

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Core Concepts

Stream ProcessingLambda ArchitectureAnalytics