System requirements

Functional:

1. Convert a long url into a short url
2. Customers can create custom URLS (if taken auto-create)
3. Min=5 chars, Max=10 chars
4. Clicking on the short url redirects to the long url
5. URL's do not expire (unless manually deleted or set exp)
6. User Auth
7. UI

Non-Functional:

1. Capture metrics/Monitoring and Logging (Number of clicks, geographic location of the click, referral sources, etc)
2. API integration
3. Performance

Capacity estimation

Estimate the scale of the system you are going to design...

API design

Define what APIs are expected from the system...

/shorten - POST

/metrics/{shortenedUrlId} - Get

/delete/{shortenedUrlId} - DELETE

/user/{userId} - GET

Created By | Full URL | Shortened URL | Date created | Exp Date? | Times clicked

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...

URL Mapping table

Metrics Table

User Table

Custom Alias

High-level design

Client contains view and and controller

View has a component to create shortened URLS

View has a component to display all urls created by that user

Controller is used to Get url and metrics data, Post new URLs, and Delete existing URLS

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...

Text field to enter the full URL

Optional text field to add custom text

Button to generate shortened URL

Button click calls the controller which will POST to the server

Server returns 200 and shortened URL which will be displayed

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?