System requirements
Functional:
List functional requirements for the system (Ask the chat bot for hints if stuck.)...
Users should be able to compose and share tweets
Users should be able to read tweets from other users
Users should be able to like tweets
Users should be able to update or delete tweets
A tweet should be less than 280 characters
Tweets can be public or private with a list of allowed viewers
Non-Functional:
List non-functional requirements for the system...
High availability
eventual consistency
scalability
durability
Capacity estimation
Estimate the scale of the system you are going to design...
storage = 200million users * 500B * 1 tweet/day * 365 days * 5years * 3 replicas
download/write = 200 million users * 500 B * 1 tweet/day / 24h / 3600s
upload/read = download * 10
API design
Define what APIs are expected from the system...
POST /api/v1/tweets
POST /api/v1/likes/{tweetId}
DELETE /api/v1/tweets/{tweetId}
PUT /api/v1/tweets/{tweetId}
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...
Table User:
UserId(primary key)
hashed password
Table Tweet:
TweetId(primary key)
UserId
CreatedTimestamp
LastUpdatedTimestamp
TweetContent
Privacy
allowedViewers
Table like:
UserId
TweetId
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...
if a celebrity sends a tweet, pull
if a tweet is sent by non-celebrity, push
Trade offs/Tech choices
Explain any trade offs you have made and why you made certain tech choices...
database replicas, use sharding; shard by userId can use hotspot problems, but sharding by itemId can cause reading several shards for one user
Future improvements
What are some future improvements you would make? How would you mitigate the failure scenario(s) you described above?