Jack has provided the following feedback on your session:

Kwan demonstrated strong clarity and initiative in breaking down the system design for a payment platform. The session covered key aspects including requirements, API design, high-level components, and scalability strategies.

Areas of strength included:

• Quickly enumerated core functional and non-functional requirements
• Clearly identified key entities and drew distinctions between Payment and Transaction
• Completed a comprehensive API definition and began expanding entity schemas
• Demonstrated some deep dive around data correctness guarantees — aim to confidently frame how at-least-once delivery + deduplication = exactly-once semantics for hold, charge and settlement phase
  
  

Areas for improvement:

• Considered idempotency with a composite deduplication key strategy
• Discussed scalability with sharding and CDC-based state syncing
• Include payment settlement as a distinct functional requirement early on
• Clarify durability guarantees (e.g., traceability of failed transactions, state recovery post-crash)
• Embrace more collaborative moments with your interviewer—for instance, naturally inferring steps like DB validation during payment creation

Overall, Kwan shows great structure and promise in system design interviews. With additional work on durability, correctness, and deeper tradeoff thinking (especially in Staff+ topics like failure modes, encryption and collaboration signals), they’ll be well-positioned for success in senior-level interviews.