Design short URL service with click counting

Design a production-ready service that:

1. Creates a short URL for a given long URL (URL shortening).
2. Redirects when a user visits the short URL.
3. Maintains a click counter (number of times each short URL was visited), queryable via an API.

Functional requirements

• POST /shorten takes a long URL and returns a short code + short URL.
• GET /{code} redirects (HTTP 301/302) to the long URL.
• GET /stats/{code} returns:
  • total click count
  • optionally breakdown by time bucket (e.g., per day) if feasible

Non-functional requirements

• Very low latency for redirects.
• High availability.
• Must scale to high QPS (both reads and writes).
• Prevent obvious abuse (spam/DoS).

Clarifications to address

• Custom aliases? Expiration?
• Idempotency (same long URL returns same code or always new)?
• Consistency expectations for click counts (exact vs eventually consistent).