📌  links of videos and materials that will can help you out to refine and become a pro at this sys design question (visual explanations and diagrams are 🔥 there so have a look as this is smth you’ll need in your interviews):

• https://systemdesign.one/url-shortening-system-design/
• the actual book chapter: https://archive.org/details/system-design-interview-an-insiders-guide-by-alex-xu-z-lib.org/page/n119/mode/2up
• of course our favourite dude, Jordan has no life on YT explains it perfectly: https://www.youtube.com/watch?v=5V6Lam8GZo4

all n all a URL shortener is a service that converts long URLs into shorter, more manageable links. It's widely used for various purposes, including social media sharing, tracking click-through rates, and improving user experience.

Okay, let's delve deeper into each section of the "Design a URL Shortener" chapter summary to provide a more comprehensive understanding.

Key Requirements

Beyond the basic requirements, a robust URL shortener must also consider:

• Analytics: Tracking click-through rates, geographic distribution of clicks, and the platforms (e.g., mobile vs. desktop) from which clicks originate can provide valuable insights.
• Security: Protecting against malicious use, such as shortening URLs that redirect to phishing sites or malware distribution points, is crucial. This may involve implementing blacklists and reporting mechanisms.
• Customization: Allowing users to create custom short URLs (e.g., example.com/my-brand) enhances brand recognition and user experience.
• Expiration: Providing options for setting expiration dates on shortened URLs ensures that links remain relevant and avoid directing users to outdated content.
• Update target URL: Provide a mechanism to update a shortened URL target to redirect to a different destination, keeping the short link alive

API Design

The API endpoints are the gateways to the URL shortening service.

1. Shortening API (POST /shorten):
   • Request Parameters:
     • long_url (required): The original, long URL that needs to be shortened. Input validation is essential here to ensure the URL is properly formatted and accessible.
     • custom_alias (optional): A user-specified short URL. The system needs to check for uniqueness before assigning it.
     • user_id (optional): Identifies the user making the request, enabling tracking, custom URL management, and rate limiting.
     • expiration_date (optional): A date/time after which the short URL will no longer redirect.
   • Response:
     • Success (200 OK): Returns the newly created short URL.
     • Error (400 Bad Request): Indicates invalid input (e.g., malformed URL, invalid custom alias).
     • Error (409 Conflict): Signals that the requested custom alias is already in use.
     • Error (429 Too Many Requests): Indicates that the user has exceeded their rate limit.
2. Redirection API (GET /{short_url}):
   • This is a simple GET request to the short URL.
   • The server should respond with an HTTP 301 (Permanent Redirect) or 302 (Temporary Redirect) status code, along with the Location header set to the original long URL. The choice between 301 and 302 depends on whether the redirection is considered permanent or temporary. 301 is better for SEO as it passes link juice.
   • Error (404 Not Found): If the short URL does not exist or has expired.

Data Model

The database schema is the foundation of the service.