System requirements

Functional:

[file]

• upload files
• download files
• view file list
• move file
• edit file name
• delete files

[folder]

• create folder
• move folder
• edit folder name
• delete folder

[advanced function]

• sync files
• share file link
• manage file version

Non-Functional:

Scalability

Availability

Security

• unauthorized user can't view and edit and delete from shared link

Capability

• system can process large file

Reliability

Fault Tolerance

Capacity estimation

• user : 1M
• data : 2G/month = 67M/day
• data in a day = 1M*67M = 67TB/day

API design

POST /api/v1/file/upload?

Database design

[file_metadata]

id, integer, primary key

version, Integer

name, String

size, double

createdAt, timestamp

createdBy, String

updatedAt, timestamp

High-level design

sync service

client app

• detect file changes
• upload file by chunk

file storage

• we should use distributed file system like s3 that's going to store and replicate data in a reliable way

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

• conflict resolution
  • automatic resolution : two user edit different line
  • manual resolution: two user edit same line
• sync file
  • delta sync
  • only sync chunk whose hash is changed

Trade offs/Tech choices

• mongoDB
  • good : scalability
  • bad : eventual consistency
• Active-Passive multi AZ
  • good : Strong consistency
  • good : simple fail-over
  • bad : useless standby instance for ideal situation

Failure scenarios/bottlenecks

mongoDB failure

• multiAZ DB
• circuit breaker

S3 failure

• multi region repllication

API server bottleneck

• multi LB
• rate limiter setup at nginx

Future improvements

What are some future improvements you would make? How would you mitigate the failure scenario(s) you described above?