System requirements


Functional:

List functional requirements for the system (Ask interviewer if stuck)...

  • Generates a unique shortcode
  • Short code is associated with long URL in database
  • Accessing short url looks up short code in database to retrieve long URL
  • Long URL is returned to user and user is redirected



Non-Functional:

List non-functional requirements for the system...

  • Short code generation should be quick




Capacity estimation

1 million URLs a day = 11 URLs per second

100 million URL short code look ups a day = 1160 short code look ups a day

Assuming it runs for 10 years, this means we must support 3.65 billion short codes



API design

POST api/v1/createShortUrl:

  • request parameter: longUrl
  • returns shortURL


GET api/v1/getLongUrl:

  • request parameter: shortUrl
  • statusCode: 301
  • location: longURL




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?