System requirements

Functional:

1. Register user
2. Login
3. Update portfolio
4. Compose tweet
5. Get tweets
6. Update tweet
7. Delete tweet
8. Favorite tweet
9. Unfavorite tweet
10. Follow other users
11. Unfollow other users

Non-Functional:

1. Availability over consistency
2. Distributed system
3. Scalability

Capacity estimation

DAU: 10 million users

Tweets: 10 million tweets/day

100 reads / tweet

Average: 500 bytes/tweet

Tweets created per second: 10 million tweets/day / 24 hours/day / 60 min/hour / 60 sec/min = 1 * 10^7 / 1 * 10^5 = 100 writes/second

Estimate max tweets created per second: 2*100 = 200 writes/sec

Tweets read per second: 100 * 100 = 10,000 reads/second

Max tweets read per second: 2* 10,000 reads/second

Daily storage without media: 10 * 10^6 * 500byte = 5* 10^9 B = 5 TB

API design

1. Register user takes email and password
2. Login (takes email and password)
3. Update portfolio takes (userId, portfolio)
4. Compose Tweet (userId, content, createDate, updateDate)
5. notifyUsers(takes the tweet object which include userId)
6. getTweet(tweetId)
7. getTweets(userId)
8. Update Tweet(tweetId, content, updateDate)
9. Delete Tweet(tweetId)
10. Favorite Tweet(userId, tweetId)

Database design

Register user, login, and update portfolio endpoints will mainly interact with the USER table.

Create, Get, Update, and delete tweets with interact with TWEET Table, and User table.

When trigger follower and notify we will interact with the FOLLOW table.

When favorite a tweet will interact with FAVORITE table

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?