System Design: End-to-End Architecture Walkthrough

Prompt

Whiteboard the end-to-end architecture of a complex, user-facing system you led. Cover:

1. Major components and their responsibilities.
2. Data flows and key interactions (happy-path and failure-path).
3. Storage choices and data models (including consistency needs).
4. External dependencies and how you integrated with them.
5. Key trade-offs (e.g., consistency vs. availability, latency vs. cost).
6. Scaling strategy and failure recovery/resiliency patterns.
7. Testing, monitoring/alerting, and iteration practices.
8. What you would change if you rebuilt it today.

Minimal Context (to keep the exercise concrete)

Assume a high-availability, low-latency service with the following example constraints:

• p99 latency: ≤ 300 ms for synchronous APIs.
• Availability: ≥ 99.95%.
• Peak load: ~2,000 requests/sec (bursty), average ~300 requests/sec.
• Multi-region read traffic; write traffic primarily in one region initially.
• Mix of strongly consistent operations (e.g., money movement, ledgers) and eventually consistent operations (e.g., analytics, notifications).

If you don't have a past project that fits, you may use a representative example such as "Real-time transaction authorization and settlement" or "High-traffic quotes and checkout service."