Design ad click aggregator and file sync service

You have two system design prompts.

1) Design an ads click aggregation system

Design a service that ingests ad click events at very high QPS and supports aggregated analytics.

Functional requirements

• Ingest click/impression events (at least clicks; optionally impressions) from multiple frontends.
• Provide near-real-time aggregates such as:
  • clicks per ad_id / campaign_id / advertiser_id
  • breakdown by time window (e.g., per minute, per hour, per day)
  • optionally by country/device
• Support querying these aggregates via an API (and/or dashboard).

Non-functional requirements

• High write throughput; scalable horizontally.
• Handle duplicates and retries (idempotency).
• Handle late/out-of-order events.
• Clearly define consistency/latency targets (e.g., “within 1–5 minutes”).

2) Design a file storage + sync service (Dropbox-like)

Design a cloud file sync product where users can upload files, keep folders in sync across devices, and share files.

Functional requirements

• Upload/download files and list folders.
• Sync changes across multiple devices (near real-time).
• Versioning (recover older versions) and deletion/restore.
• Sharing via link and/or ACL-based sharing.

Non-functional requirements

• Large files support (chunking/resumable upload).
• Efficient storage (dedup/content-addressing acceptable).
• Security (authn/authz, encryption).
• High availability and scalability.

For both prompts, explain APIs, data model, major components, scaling strategy, and key trade-offs.