Requirements

Functional Requirements:

• Generate alias and redirect to original URL
• Handle 404 Not found requirement
• Should handle only base62 chars with length of 7
• Support configurable link expiration (TTL); expired returns 404

Non-Functional Requirements:

• System handle 100M DAU
• 100M writes per day
• 10B reads per day
• System should have acceptable latency
• Validate scheme + host at API layer
• Do not verify destination reachability at creation time

Writes: 100M / 86400 = 1.2k writes/sec avg

Reads: 10B / 86400 = 115 reads/sec avg

Storage over 5 years: 100M urls/day x 362 = 36.5B urls/year x 5 x 500 bytes = 91TB of raw data

API Design

• Read API to redirect user
• Write API to create url shortener

High-Level Design

Reads dominate. We should not have a single database, so we should have multiple read replicas with a load balancer between the cliente and the server

Database Design

Define the data model. Identify the main entities, their attributes, and relationships. Consider the choice of database type (SQL vs NoSQL) and justify your decision based on access patterns...

Detailed Component Design

Deep dive into 2-3 key components. Explain how they work, how they scale, discuss tradeoffs, capacity, and any relevant algorithms or data structures.