System requirements

Functional:

URL creation:

• User provides a target URL as input
• Convert the URL into a short URL
• Store the short URL and the target URL as a pair in the Database

Short URL usage:

• User uses the short URL
• Select the short URL in the database and retrieve the target URL
• Send a redirect from short to target URL

Non-Functional:

• Shall be able to handle 6000 users per minute
• Sub-second response time for a request

Capacity estimation

As the given compute requirements are not very high the hardware requirements are correspondingly low. It is more crucial to have the right architecture, like a micro-services architecture which allows to properly scale and serve 6000 users per minute. So horizontal scale is more important than vertical scale.

Per request we need a DB access either for storing an URL pair when an original URL is shortened or for reading the original URL based on the short URL for the redirect. We must ensure enough DB connections are available as this might be more likely to become a bottleneck than serving the requests as such. For the redirect case we should think about introducing a cache to minimize the no. of DB accesses.

API design

Object: ShortURL

Methods:

• shortURL.create(targetURL) - returns shortURL as string
• shortURL.resolve(shortURL) - returns targetURL as string

Database design

The main DB table is basically a key value pair with the short URL as primary key and the original URL as value. As the redirect case will happen more often the short URL as key makes sense to allow optimal read performance.

High-level design

We need a server who hosts the Client web pages and the URL shortening service. In between shall be a load balancer to balance the request load and implement basic security features like DOS prevention etc.

As persistence of the short URL matching the original URL we need a database. A Cache is also recommended to minimize DB load for the redirect case and increase request performance.

Request flows

Explain how the request flows from end to end in your high level design. Also you could draw a sequence diagram using the diagramming tool to enhance your explanation...

Detailed component design

Dig deeper into 2-3 components and explain in detail how they work. For example, how well does each component scale? Any relevant algorithm or data structure you like to use for a component? Also you could draw a diagram using the diagramming tool to enhance your design...

Trade offs/Tech choices

Explain any trade offs you have made and why you made certain tech choices...

Failure scenarios/bottlenecks

Try to discuss as many failure scenarios/bottlenecks as possible.

Future improvements

What are some future improvements you would make? How would you mitigate the failure scenario(s) you described above?