Design an Accurate Click Aggregator
Company: Apple
Role: Software Engineer
Category: System Design
Difficulty: medium
Interview Round: Technical Screen
Design an ad click aggregation system.
The system receives click events from multiple sources, including web, mobile apps, and TV devices. It must ingest a high volume of click data, handle duplicates and retries, and produce accurate aggregated click counts for downstream analytics and reporting. Accuracy is a primary requirement.
Discuss:
- the event schema or API contract
- the ingestion pipeline
- how to normalize data from different client sources
- how to deduplicate events and avoid overcounting
- how to aggregate counts by dimensions such as ad, campaign, source, and time window
- storage choices for raw data and aggregated results
- how to handle late or out-of-order events
- how to scale the system while preserving correctness and availability
Quick Answer: This question evaluates a candidate's ability to design reliable, high-throughput event processing and analytics systems, emphasizing data modeling, ingestion, deduplication, aggregation, and correctness under scale with a primary focus on accuracy.