Requirements

Functional Requirements:

• Shortening a URL
• Redirecting user from a short URL to the original URL (long)

Non-Functional Requirements:

• Scalability - handle millions of URL shortening and redirection requests
• Latency - redirects user from a short URL to long URL quickly
• Availability - maintain very high uptime, especially for redirecting functionality

Capacity Estimation

Traffic Consumptions

• 200 RPS for creating short URL
• 20,000 RPS for redirecting short URL to long URL

Storage Requirement

• Long URL - 100 bytes
• Short URL - 8 bytes
• Creation Time - timestamp - 8 bytes
• Created By User ID - 20 bytes
• Expiration Time - timestamp - 8 bytes

Each entry total 144 bytes rounding it to 256 bytes of simplicity

Daily storage = 200 * 256 * 24 * 60 * 60 = 4.4 GB/day

Five year storage = 5 * 365 * 4.4 GB = 8 TB

Adding a buffer for growth, hence rounding it to 15 TB for 5 years

API Design

• shortenUrl() -> will accept long url as input and short url as output
• redirectUrl() -> will accept short url as input and return HTTP 302 redirect to original URL

High-Level Design

Database Design

Primary data model for URL shortener is a mapping between short and long URLs. This system has:

• Simple queries - most operations involves basic lookup or inserts
• String consistency - once a mapping is written, it must be visible to all readers
• Read heavy traffic -> far more redirects occurs than url generation

A key value store like Dynamo DB is a natural fit. Dynamo DB provides horizontal scalability, high performance and optional strong consistency

Detailed Component Design