System requirements

Functional Requirements:

1. Shorten URL: The service should generate a short URL that redirects to the original URL.
2. Redirect: When a short URL is accessed, it should redirect to the original URL.
3. Analytics: Users should be able to see analytics for their shortened URLs, such as click counts and referrer information.
4. Custom Alias: Users should have the option to create a custom alias instead of a random one.
5. Expiration: URLs can be set to expire after a specific time or after a certain number of uses.
6. User Accounts: Users can create accounts to manage their URLs, view statistics, and customize links.
7. API Access: Provide an API for developers to integrate the URL shortening functionality into their applications.

Non-Functional Requirements:

1. Scalability: The service should handle a high volume of requests as user traffic grows.
2. Performance: Short URL redirection should occur in milliseconds, to provide a smooth user experience.
3. Reliability: The service should have high availability and uptime, ensuring URLs are consistently accessible.
4. Security: Protect against malicious use, such as spam and phishing links.
5. Data Durability: Ensure that the stored original URLs and their associated data are not lost.
6. User-Friendly: The interface should be easy to use for both regular users and developers using the API.

Capacity estimation

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

Average User Base 1 million

Per User Generate about 10 Url per year

Write to Read ratio 1:100

URL generated per year 10 million/year

Url read per year 1 billion/year

QPS 3

RPS 300

storage estimates

3 * 1 KB * 31*10^6 = 100 GB

For click analytics =100GB * 100 =10 TB

Peak QPS 15

Cache 300*86400*1KB = 25GB

API design

ShortenUrl(apidevkey,originalUrl,alias,expiration)

RedirectUrl(apidevkey,shortUrl)

302 redirect to capture all those analytics related stuff

Analytics(apiDevKey,shortUrl)

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...

UserTable(userid,password,address,email)

ShortenUrlTable(custom_url,original_url,alias,expiration)

analyticsTable(custom_url,region,timestamp)

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...

High Level Design

It will have client

It will have loadbalancer to balance the high traffic

It will have apigateway for authorization,ratelimiting,authentitcation

Microservices will be UserReg,authentication,Analytics,shortenMicroservice

Then there will be db to store all the shorthand url

MemCache or redis to get frequently access url 

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?