Whiteboard and Deep Dive a Past Project

Quick Overview

This question evaluates a candidate's end-to-end system design skills, including architecture decomposition, trade-off analysis, data consistency choices, scalability and resiliency patterns, and integration of operational practices for a user-facing distributed service.

System Design: End-to-End Architecture Walkthrough

Prompt

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

Major components and their responsibilities.
Data flows and key interactions (happy-path and failure-path).
Storage choices and data models (including consistency needs).
External dependencies and how you integrated with them.
Key trade-offs (e.g., consistency vs. availability, latency vs. cost).
Scaling strategy and failure recovery/resiliency patterns.
Testing, monitoring/alerting, and iteration practices.
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."

Whiteboard and Deep Dive a Past Project

Quick Overview