System requirements

Functional:

• User should be able get register a contest
• User should be able to submit solution to a problem
• User should be able test run against test cases
• User should have ability to submit in multiple languages.
• User should be able to view leaderboard or his/her rankings.

Out of Scope:

• Debug the code submitted by user
• Notes capability for each problem
• User profiles
• User authentication
• Social features
• Payment processing

Non-Functional:

List non-functional requirements for the system...

• System should return submission results within 5 secs
• View contests and problems and submitting them should be highly available.
• From consistency point, rank or ratings can be eventually consistent
• Malicious output should be filtered before submitting code for evaluation
• At peak time, contest should be able to take load of 100k viewers.

Capacity estimation

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

Total number of users = 500k

Total number of active users = 200k

During peak hours which is during contests, users can go up to 100k

During peak hours one user submits around 10 solutions in an hour; with 100k users it would be 100k * 10 = 1 million submissions per hour ~ 1000 submissions per second.

Storage wise it should not be concern as for 200k users * 10 submission(every day) * 365

Size of submission: less 5Mb

10 **12 bytes of data would be used every year; which is manageable from scalability point of view

API design

Define what APIs are expected from the system...

1) Registration for Contents

POST /user/contest/register

Input:

{

contestId,

}

Output:

{

message: "User Registration successful/ or not

}

No user id is provided due to security concerns as it can be obtained through sessionId or some sort of token

2) Submitting the solution

POST /user/contest/submit/:contestId

{

problemId

codeText

language: ( from dropdown)

}

{

status

AdditonalText:

NumberOfTestsPassed

}

3) Running the solution

POST /user/contest/run/:contestId

{

problemId

codeText

language (dropdown)

}

{

status: List ( Result for each test)

}

4) GET /contest/rankings/:contested

{

user: Partial ( in paginated fashion)

problemResult : List

}

Database design

User

• userId
• country
• ....

Registration:

• userId
• contestId

Contest

• id
• List of problems - problemId

Problem:

• id:
• testCases: s3-location
• contestId - not mandatory

Submissions:

• id
• userId
• problemId
• Score

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?