Design a Courier Payout Service

1. Problem Statement

2. Architecture Discussion Map

Use this as one discussion aid, not a single correct answer. Your design should follow from the requirements, scale, and trade-offs you establish.

graph LR
    A["Design a Courier Payout Service"]
    A --> F1["Payout API and rule modeling"]
    A --> F2["Idempotency and duplicate requests"]
    A --> F3["Upstream latency and retries"]
    A --> F4["Money precision and audit history"]
    A --> F5["Testing changing compensation rules"]

3. Key Focus Areas

• 1
  Payout API and rule modeling
• 2
  Idempotency and duplicate requests
• 3
  Upstream latency and retries
• 4
  Money precision and audit history
• 5
  Testing changing compensation rules

4. What the Interviewer Looks For

The interviewer probes these areas, and the report grades the interview against them.

• API contract and idempotency
• Money arithmetic and rule modeling
• Upstream dependencies and input snapshots
• Adjustments, recomputation, and audit
• Logic walkthrough and test plan

5. What Strong Candidates Should Demonstrate

• Turn compensation rules into deterministic, testable calculations.
• Make payout creation idempotent and auditable.
• Handle slow or unavailable upstream order services.