System requirements

Functional:

• User can provide a url for which it receives a shortented url
• Shortented url should direct to the desired page.

Non-Functional:

• Minimum latency

Capacity estimation

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

Total life expetancy: 5 years

Users: 10 million

assuming 100 million unique short urls

1 billion redirections = 7 requests/sec

storage req: 100 million * 371 byes - 37.1 GB

API design

Define what APIs are expected from the system...

POST /api/v1/shorten-url/ 201 {data={"url": ""}} response={"shortened_url=""}

GET /api/v1/redirect-url/

302 - if expiration is required

301 - if no expiration

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...

Model urls {

id pk,

created_at TIMESTAMP,

url VARCHAR(255),

shortened_url VARCHAR(100),

expire_at TIMESTAMP

}

• Can have partitioned tables and stop querying the older ones

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 -> alb -> server -> (cache) -> database

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...

For POST /api/v1/shorten-url/ 201 {data={"url": ""}}

• No auth middleware
• validate url using regex (fast approach)
• calculate expiration timestamp
• append expiration timestamp to url string and hash the string using MD5 hashing algorithm (fast, security is not a concern here)
• get_or_create database call
• return shortened url

For GET /api/v1/redirect-url/

• read hash for url from query-params
• make a db call to get url and return with 301 or 400 checking expiration time

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...

• MD5 is fast but not collision resistant

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?

• Login based
• Tracking activity