System requirements

Functional:

List functional requirements for the system (Ask the chat bot for hints if stuck.)...

• Given a long URL, the service should generate a shorter and unique alias for it.
• When the user hits a short link, the service should redirect to the original link.
• Links will expire after a standard default time span.

Non-Functional:

List non-functional requirements for the system...

• The system should be highly available. This is really important to consider because if the service goes down, all the URL redirection will start failing.
• URL redirection should happen in real-time with minimal latency.
• Shortened links should not be predictable.

Capacity estimation

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

Write operation: 1,000 URLs are generated per second.

Read operation: 10,000 URL visits per second.

Assuming the URL shortener service will run for 10 years, this means we must support

1,000*60*60*24*365*10=315 billion records

Assume average URL length is 100.

Storage requirement over 10 years: 315 billion * 100 bytes = 31.5 TB

API design

Define what APIs are expected from the system...

1.URL shortening. To create a new short URL, a client sends a POST request, which contains

one parameter: the original long URL. The API looks like this:

POST api/v1/data/shorten

• request parameter: {longUrl: longURLString}

• return shortURL

2.URL redirecting. To redirect a short URL to the corresponding long URL, a client sends a

GET request. The API looks like this:

GET api/v1/shortUrl

• Return longURL for HTTP redirection

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...

Users: Store user information if user accounts are required.

URLs: Store original URLs and their corresponding short URLs.

Clicks: Track clicks on the shortened URLs for analytics.

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. If you are unfamiliar with the tool, you can simply describe your design to the chat bot and ask it to generate a starter diagram for you to modify...

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?