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*clients include both mobile and web
*iOS team has 3-5 devs
*100K to 500K DAUs worldwide
*send & receive money between users -> POST /transactions
*transfer money between accounts for a single user -> POST /transaction
*account management (CRUD): name, type, balance -> PUT/POST /accounts/id
*multi-currency support: pay in USD, receive in EU, rate should be consented before committing
*fraud detection: alert of suspicious user account before sending money to another user
*buyer and seller protection: money back guarantee (within 30 mins) if both parties are verified
*view transaction history sorted based on time (latest first)
*push notification for e.g. receiving money from another user
*Scalability: support huge user base from worldwide
*Performance esp. when internet connection isn't always good
*privacy
*security
out-of-scope:
*real-time
*authentication: assume logged-in
Estimate the scale of the system you are going to design...
versioning header
authentication header
REST based
JSON payload
Pagination supported for long list of records such as /Transactions
POST /transactions
body: Transaction
response: 201 Created, id
GET /transactions/id
response: Transaction
GET /accounts
response: [Account]
POST /accounts/id
body: Account
GET /transactions?after=
response: [Transaction]
Transaction:
transactionID: UUID
type:
sender: UUID?
receiver: UUID?
outgoingAccount: UUID
receivingAccount: UUID
amount: Int
currency: Int
Account:
id: UUID
user: UUID
type: Int
name: String
balance: Int
currency: Int
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...
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...
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...
Explain any trade offs you have made and why you made certain tech choices...
Try to discuss as many failure scenarios/bottlenecks as possible.
What are some future improvements you would make? How would you mitigate the failure scenario(s) you described above?