System requirements

Functional:

tweet

read tweets of friends

liking a tweet

Non-Functional:

highly available

scalable

low-latency for getting tweets

Capacity estimation

100 million DAU

2 tweets per user

a tweet:

• 100 char = 500 Bytes
• media: 10mb - (500Bytes meta fata)
• 1 KB to store pre tweet

200 mill new tweets per day

200 GB * 400 * 10 = 800 TB - 1PB

100:1 reads/writes

40 k PQPS

API design

addTweet(user_id, content, media)

getTweets(user_id)

Database design

NOSQL

user

• user_id
• contact_info

post

• post_id ID
• user_id ID
• media string
• created_at time

feed cache

• user_id
• post_id

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?