System requirements

Functional:

Upload file

Replace file

Delete file

Share Link

Share access with emails

Make folder

Download file

File storage limit

Signup user

Upgrade storage

Pay for storage

View all files

Preview/play file

file versioning/search

File sync

Non-Functional:

Scalability (high number of uploads and downloads).

Availability: highly available, should basically never be down. 3 nines

Eventual Consistency (queuing is ok)

Low latency on downloads

Capacity estimation

Lots of competition so likely won't be at the billion user scale.

Estimate:

300,000,000 MAU

10,000,000 DAU

Peak concurrency: workday 1/3 of the time gets lay say half the traffic: 5,000,000 users at peak. QPS is much higher since you can open multiple requests at the same time. 10,000,000 QPS

Storage requirements;

Different file types: docs, mp3, videos. some users will only upload a day, some will be uploading many.

docs - 0.5 - 5mb

mp3- about the same

video file: 500 MB -> 50gb

Let guess a weighted average of

500 MB and 30% of trafic is write traffic 30M X 500Mb

15TB per hour x 24

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

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?