System requirements

Functional:

1. The system should be able to generate a tinyURL for a given URL
2. The system should be able to re-direct to the original URL
3. May be monitor which one is a popular URL which is being shortened

Non-Functional:

1. Low latency, there should be no latency , it should be easy to create a shortURL and seemless to re-direct to the full URL
2. Scalable
3. Highly available -- the system should be able to function even where are failures, to ensure fault-tolerance and high reliability

Capacity estimation

Let's assume total customer size is 1M

And 10% of the customer size uses the system on a daily basis ==> roughly 10000 users/ day

In which lets say there 5 reads per 1 write

Data I will store:

1. For shortening purposes: I will need the bigURL and tinyURL ( 200 + 10 ) roughly 210 bytes , let's call this DB1
2. For Monitoring purposes: I will userId which is there IP , count max of 20 bytes, let's call this DB2

Let's say all 10000 users create tinyURL ==> 10000 * 210 = 2.1 MB/ day for DB1.

For DB2 20 * 10000 is roughly 200 KB/ day

that is DB1 will be 60 MB/ month in peak times we can estimate like (60 MB * 1000/ month) roughly 60 GB

and for DB2 200 KB * 30 ==> 6 MB/ month and in peak time it will 6 GB

Both are not large boundaries

I think we can go for NoSQL for both the tables scalability, high availability and low latency

API design

string createTinyURL(UserID,BigURL)==> output will be tinURL

string getOriginal(TinyURL) ==> should return to the big URL ; if we return the original url to http response with the code that URL has been moved to a address and that address will be bigURL ; will be enough for redirect, the browser will take care of it

void deleteTinyURL(TinyURL, userId) ==> delete the tinyURL created by a user

int accessCount(UserId, TinyURL) ==> get the number of times the user has clicked and used the link

int getCount(UserId) ==> gets the count/number of times the userID has used the system

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...

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...

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?