System requirements
Functional:
List functional requirements for the system (Ask the chat bot for hints if stuck.)...
- Make payments through different modes like Bank transfer, Credit/Debit card, digital wallet
- Receive notifications of the payment made and received
- Link/Delink bank accounts, Credit/Debit cards and digital wallet accounts to send/receive money through the payment system
Non-Functional:
List non-functional requirements for the system...
- Secure and tokenize sensitive information as per international standards like PCI compliance
- Audit support. Any transaction must have an audit trail to find its origin and journey
- Replayability: It should be possible to trace operations of a transaction and verify correctness
Capacity estimation
Estimate the scale of the system you are going to design...
1000 Transactions Per Second (TPS)
Account information of linked accounts for each user will be stored. Considering a large-scale deployment of the payment system has a total of 100 million users, total data to be stored is:
- Account number or id (100 bytes)
- Card information (100 bytes)
= 1 TB approximately
Book keeping and ledger information for transactions.
API design
Define what APIs are expected from the system...
- Make payment through mode M1
POST https://
Returns 20x success + payment processing page for that method
- Add a business
POST https://
Returns 20x for success or 40x/50x for failures
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?