System requirements

Functional:

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

• Users can enter a URL that they want to shorten
• Users can specify how they would like to shorten the URL. If the URL they request is already taken, they must pick another.
• If a user enters the shortened URL into the browser, we redirect them to the longer URL.
• URL redirects must be fast.
• Error handling for cases when a user does not navigate to a valid URL.
• API support?
• Analytics page. This should show usage.
• Link expiration.

Non-Functional:

List non-functional requirements for the system...

• The front end UI must be nice and tidy!
• We need to ensure that most URLs that people want are available.
• Low latency performance
• Scalability

Capacity estimation

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

Let's say we have 1000000 users.

Each user has 1.15 URLs that they are shortening.

So we have 1150000 mappings in our database.

Each mapping should map:

• Redirect URL 50 characters

To:

• URL after redirection 50 characters
• Expiration date and metadata 25 characters

So each mapping needs 124 characters or 125 bytes.

1150000 mappings * 125 bytes = 145 megabytes of storage for mappings

Analytics data.

1150000 shortened URLS * 100 bytes of storage = 115 megabytes of storage for mappings

Total storage = 145 megabytes + 115 megabytes = 260 megabytes

API design

Define what APIs are expected from the system...

Restful API

• IsURLAvailable(URL)
• Is the url that the user is requesting available?

• CreateMapping(startingURL, mappedURL)
• Redirect(URL)

• GetAnalytics(startingURL)

Will use API keys to authenticate API requests

We will use Swagger for documenting the API.

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...

Mapping item

• Key
• Original URL
• Value
• Redirect URL
• Expiration Date

URLs Table

• Columns
• id (primary key)
• short_url (index)
• long_url
• creation_date
• expiration_date
• custom_alias
• Indexes
• short_url

I will use a NoSQL databases like GCP Datastore for flexibility and scalability.

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...

• Shortening service
• Database storage

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?