System requirements

Functional:

• The user can input a real url and get a tiny url back
• The user can set an expiration date or there is a default expiration date for the tiny url
• A user can input a tiny url and be redirected to the actual url
• The user can view analytics of urls
• The user can input a custom short url

Non-Functional:

• The system needs to be available
• The system is read-heavy and we may need to separate reads from writes
• The system needs to be fast in redirect the url in order to ensure a seamless experience

Capacity estimation

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

Let's say there are 200 requests per seconds in creating new shortened urls.

And there are 20K requests per second for redirecting from shortened to actual urls.

If the shortened url has an expiration date of 1 year, then 200 * 60 * 60 * 24 * 365 = about 7B urls stored each year

Now for the shortened url, it can be made up of lower case letters, upper case letters, and numerical digits. That's 62 characters.

Lets say a shortened url will be composed of a domain name - https://tinyurl.com/{some characters} and {some characters} will be length 6. This will give us about 60B possible short urls with our 62 characters.

So a shortened url is 6 bytes. We can append the prefix instead of storing the prefix. Lets assume the real url on average would be 200 bytes. So 7B * 204/1000/1000/1000 = about 1.5 TB

API design

POST /url/shorten

input: {

real_url: ""

expiration_date: optional

custom_short_url: optional

}

output: {

short_url: ""

original_url: ""

}

GET /

This api will return a redirect

Database 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. 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...

urls table

short_url

original_url

timestamp

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?