🏗️ High-Level Design (HLD) for Url Shortener

 Goal: Convert long URLs into short unique codes, and redirect users when they visit the short link.

Key Requirements

• Functional:

  • Shorten a long URL → return a short URL.

  • Redirect short URL → original long URL.

  • Handle high read/write traffic.

• Non-functional:

  • High availability.

  • Scalability (millions of URLs).

  • Low latency.

Architecture Components

• API Gateway → handles requests (POST /shorten, GET /{shortCode}).

• Application Service → generates short codes, stores mappings.

• Database → stores mapping of shortCode → longURL.

• Cache (Redis) → fast lookups for popular URLs.

• Load Balancer → distributes traffic across servers.

Flow

1. User sends long URL → API Gateway.

2. Service generates short code (e.g., base62 encoding).

3. Store mapping in DB + cache.

4. Return short URL (tinyurl.com/abc123).

5. On access, lookup short code → redirect to original URL.

👉 This is the big picture: what modules exist, how they interact.