Requirements

Functional Requirements:

• Create a short URL for a given long URL.
• Return the long URL associated with a given short URL.

Non-Functional Requirements:

• System shall have high availability as the shortened URL may be accessed in a variety of environments or scenarios
• System shall be reliable and performant, minimizing any additional latency added to the URL loading proces

API Design

1. (POST) /<url>/shorten
   1. Stores the newly shortened URL
   2. Request format - The client provides the long URL and some piece of information that can prove that they are the owner/host of the URL. Once successful, the URL will be associated with a unique ID. Once the URL has an ID, it is in the database and duplicate URLs may not be made.
   3. Response format: 200 if successful, 403 if not authorized, 500 if invalid data or if a duplicate already exists.
2. (GET) /<url>/info
   1. Allows the web host to retrieve their shortened URL as needed. Promotes availability for the host.
   2. Request Format: The long URL and authorization info.
   3. Response format: 200 if successful, 403 if not authorized, 500 if invalid data. Consistent with the POST payload requirements
3. (GET) /<url>/redirect
   1. Redirects the end-user to the shortened URL if available
   2. Request Format: The shortened URL.
   3. Response format: 200 Success and logic triggering the redirect occurs. 404 if error, 403 if unexpected headers are provided

High-Level Design

-User and Client feed through an API Gateway containing two base services: The shortening service and the Redirect service.

-The shortening service contains the business logic for creating the shortened URL as well as the mapping between actual and shortened URL.

-The redirect service is used when the end-user enters the shortened URL in their browser. It effectively redirects them to the correct web page using the shortened URL.

-The database is where the mapped URLs (long and short) are stored. If the service is to be implemented around the globe, a CDN or distributed architecture may be considered

• Caching may also be done through the CDN.

Detailed Component Design

Key Components:

-API Gateway: Multi-functional gateway that directs both user and client (web host) requests. For the host, it allows them to create, get, or configure a shortened url. For the user, it directs them to the redirect service, which checks for the destination in the CDN Cache as well as the database.

-Database: Stores the shortened URLs, ids, and the original URL. Contains the mapping between the original URL (destination) and the shortened one. Two databases may be considered as well -- one for the shortening service and one for the redirect service.

-Shortening service: allows for the shortening of URLs and storage of the mapping between the original version and the shortened version in the database.

-Redirect service: Redirects the user by first checking the CDN cache for a more performant redirect if they have used the URL before. If not, the database is queried for the URL mappings and the redirect logic is then applied, sending the user to their intended destination.