System requirements

Functional:

Given a long url, our system should be able to identify whether the url has already been shorten, if so, return its short url, otherwise assign a new short url for it and return the short url.

Given a short url, our sytem should be able to return its long url if it exists in our system, otherwise return error message like unknown short url.

Non-Functional:

high availablity

scalability

Capacity estimation

100K users * 100 URLs = 10 million URLS

10 million URLS * 100 bytes = 1000 million bytes = 1 million KB = 10000 MB = 10 GB

API design

String getShortURL(String longURL)

String getLongURL(String shortURL)

Database design

Defining the system data model early on will clarify how data will flow among different components of the system. Also you could draw an ER diagram using the diagramming tool to enhance your design...

High-level design

You should identify enough components that are needed to solve the actual problem from end to end. Also remember to draw a block diagram using the diagramming tool to augment your design...

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?