System requirements

Functional:

• User should be able to provide a url
• Might need to validate user input (check url is valid)
• Tool should return a short version of the url (6-8 characters)
• Tool should maintain list of short urls and ensure the same short url isn't assigned to multiple long urls
• The tool should redirect traffic from the short url to the long url (by registering the short url to a DNS server?)
• User should be able to log in to their account and see the url's they've created
• User should be able to delete url's they have created

Non-Functional:

List non-functional requirements for the system...

• Tool should have fast response time (less than a second)
• Availability: Should have 99.9% uptime
• Scalability: should support thousands of users per second

Capacity estimation

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

• 8000 requests per second
  • 3000 redirection requests
  • 5000 url creation requests

More write requests than read requests

API design

Define what APIs are expected from the system...

createUrl: takes a long url link, produces a short url

validateUrl: validates short url link

createShortUrl: uses a hashing sequence to create a url that doesn't conflict with existing short urls in the database

userLogin: authentication sequence for user to log into service

deleteUrl: user should be able to delete one of their created urls

redirectTraffic: directs traffic from short to long url

shortenUrl REST Api: make a post request to this endpoint with long url, and get a short url in response

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...

We can use a NoSQL database like dynamodb for fast reads and writes. the fields are url id, short url, long url, user_id. We can use a cache like memcache or redis to cache frequently accessed urls

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...

client will make a post request to shortenUrl to get a short url. The API will handle collisions (making sure urls are unique)

for scalability, the client request will go through a load balancer, that will distribute traffic among many servers. These servers will handle the post request

Then, the server will post to the dynamodb database. the fields are url id, short url, long url, user_id

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...

We can have primary and secondary databases for more scalability.

Since we have more writes than reads, we can use asynchronous replication to update the database.

To allow this service to work globally with low latency, we can use a CDN like AWS cloudfront. This distributes traffic requests to servers in availability zones closer to the user for faster response time.

We can handle collisions by encoding each short url with with a hashed key, and checking for that key in the database before adding a new short url to the database

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?