System Design: 3-Day High-Traffic Donations Platform

Context

Design a donations platform to support a time-bounded, high-traffic fundraising campaign that runs for exactly three days. The platform must accept payments reliably at large, spiky volumes; display real-time progress and leaderboards; and cleanly start/stop at the scheduled times. Assume web and mobile clients.

What to Deliver

1. Functional requirements
   • Donation flow (intent, authorization/capture, receipts), refunds/chargebacks
   • Matching gifts and caps, leaderboards and real-time counters
   • Scheduled start/end behavior and gating
2. Non-functional requirements
   • Throughput targets, availability/SLOs, latency, cost considerations
3. System components and architecture
   • API gateway, payment processor integration
   • Idempotency and retries, fraud detection, rate limiting
   • Data model, analytics/events, real-time counters
4. Cross-cutting concerns
   • Handling traffic spikes, multi-region readiness
   • Storage choices; consistency vs durability trade-offs
   • Observability and auditing
5. Rollout plan
   • Load testing strategy, canary/feature-flag rollout, game-day readiness

Keep the design pragmatic for a three-day event while ensuring financial correctness and user trust.