Requirements

Functional Requirements:

• Create a short URL for a given long URL.
• Return the long URL associated with a given short URL.
• Redirect the short URL to the long URL
• Login and sign up
• View link analytics
• Delete saved URLs
• Payed subscription

Non-Functional Requirements:

• Redirection must happen under 1 second
• System must be high-available (99.9)
• System must provide horizontal scalability, in case an URL goes viral

Capacity Estimation

Estimate the scale of the system. Consider daily active users, read/write ratio, storage requirements, bandwidth, and any relevant QPS calculations...

API Design

• Create URL (POST) {long_url} - returns short url
• Get long URL (GET) {short_code} - returns a redirection
• Delete URL (DELETE) - {url_id} - returns OK
• Home (GET) - returns home.html

High-Level Design

The application would be a simple CRUD, with a frontend, a backend, and a database.

Given the simplicity of the application the frontend could be a static website delivered by Nginx, but it should be considered a React app if login, signup and payment will be implemented in the future.

The backend could be Express.js as it is a simple framework and fast to develop and it uses the same language as the frontend.

The database would be PostgreSQL and Redis for caching.

We should consider several options for deploying. As it is right now, this could be deployed in a Cloud VM with Docker Compose, but if we need availability and escalability, Kubernetes is a must. But k8s clusters are very expensive, so I wouldn't recommend it until we have paid subscriptions implemented. I also recommend databases to be cloud hosted.

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.