Design Short URL Service

Design a scalable URL shortening service similar to TinyURL or bit.ly. The service should provide the following APIs:

• shorten(long_url) → returns a short URL (e.g., https://short.url/abc1234)
• redirect(short_url) → returns the original long URL with a 301 redirect
• getAnalytics(short_url) → returns click statistics (clicks, referrers, countries, timestamps)

Assume 100M new URLs are created per month, with a 10:1 read-to-write ratio (1B redirects/month). The short code must be 7 characters or fewer, URL-safe, and unique. The system must handle 10K requests per second at peak, with <100ms p99 latency for redirects. Support custom aliases, expiration times, and rate-limiting per IP/user. Provide high availability (99.9% uptime) and durability. Include an async analytics pipeline that can generate real-time dashboards and batch reports.