Requirements

Functional Requirements:

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

Non-Functional Requirements:

• low latency redirects
• scale to 100M URLs
• fault tolerance

API Design

POST

admin/shortenUrl(string) -> string

admin/deleteShortcut(string) -> void

https://domain.com/[shortcut_id] -> 328 redirect to url

High-Level Design

Client can create URL shortcuts via a RESTful API with manage service. The manage service generate a shortcut id (sid) and writes the sid: url key pair to a redis instance.

Client can be redirected to URLs by navigating to the domain/[sid] url. The API Gateway handles these requests by reading the corresponding URL from the Redis database and responding with a 328 redirect with the URL. For even better performance, we can enable edge caching for popular urls on the API gateway to skip the Redis read.

Detailed Component Design

• Multiple instances of the Redis DB will be required to handle the large number of URLs and requests
• The Redis instances should be sharded by sid for even distribution
• load balancing for the manage service can be handled by round robin as the operations are simple. Rate limiting should be handled at the API Gateway to prevent overwhelming the service.
• Edge caching should cache popular urls. They should have a short time to live (1 minute) to minimize navigating to stale urls.