Design an Ad Click Aggregator

1. Problem Statement

2. Architecture Discussion Map

Use this as one discussion aid, not a single correct answer. Your design should follow from the requirements, scale, and trade-offs you establish.

graph LR
    A["Design an Ad Click Aggregator"]
    A --> F1["Real-time aggregation Count Clicks per Ad"]
    A --> F2["Correctness Advertisers must be billed correctly"]
    A --> F3["Click-ID deduplication, separate from invalid-traffic filtering"]
    A --> F4["Aggregate-store choice and rollups for advertiser queries"]

3. Key Focus Areas

• 1
  Real-time aggregation (Count Clicks per Ad)
• 2
  Correctness (Advertisers must be billed correctly)
• 3
  Click-ID deduplication, separate from invalid-traffic filtering
• 4
  Aggregate-store choice and rollups for advertiser queries

4. What the Interviewer Looks For

The interviewer probes these areas, and the report grades the interview against them.

• Semantics, scope, and estimation
• Ingestion, deduplication, and idempotency
• Event-time aggregation and late data
• Billing correctness and reconciliation
• Query serving and operations