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:

• low latency
• horizontal scaling
• fault tolerant

API Design

In the API design there are two major endpoints (following REST architecture to create these endpoints) involved which are ->

1. accepts longUrl and returns short url (POST REQUEST) -> if longUrl already exists return short url
2. accepts short url and returns long url (GET REQUEST) -> status code 301, 302 is returned with the location for redirection

High-Level Design

client makes a GET or POST call to the web servers the request reaches the load balancer based on algorithm used for load balancing traffic is distributed among different instances of application. Before a call is made to the DB a call is made to cache to see if a response is cached for that request if it is not then a db call is made and data is returned to the client and also it is cached in the cache.

Detailed Component Design

1. relational database is used to store the mapping we have 3 columns -> ID (which we generate using some methods), LongUrl, ShortUrl (to use some hash functions to generate short url)
2. client makes a POST call to web server with long url. It checks if it exists in cache if it is short url is returned. In case it does not exist makes a call to DB if entry exists corresponding short url is returned if no entry exists a new entry is created. It is cached and returned back to the client.
3. Load balancer to distribute the load to handle traffic
4. Cache like reddis can be used to store frequently accessed with TTL not being to short or too long
5. client makes a GET call to web server with short url if it exists in the cache response is returned otherwise a call is made to the db to get the corresponding long url it is cached and the response is returned.