System requirements
Functional:
Tweeting: Users should be able to post tweets, which are limited to 140 characters.
Following: Users should be able to follow and unfollow other users to see their tweets.
Liking: Users should be able to like or favorite tweets.
Home Feed: Users should have a home feed displaying a list of tweets from the users they follow.
Hashtags and Mentions: Users should be able to include hashtags and mention other users in their tweets.
Search: Users should be able to search for tweets, users, or hashtags.
Notifications: Users should receive notifications for new followers, likes, or mentions.
Non-Functional:
Performance(latency, throughput), scalability (horizontal, vertical), availability, reliability, security,
Capacity estimation
Estimate the scale of the system you are going to design...
API design
Define what APIs are expected from 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
Tweet service - writes/reads tweets
User service - handles registrations/login/profiles
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?