🌐 System Design: API Integration, Data Orchestration & Caching (Staff Engineer Interview Guide)
Category: system-design
Difficulty: hard
Target Level: Staff Engineer / Principal Engineer Duration: 45-60 minutes Interview Focus: Distributed Systems, Cache Strategies, API Design, Performance, Observability Interview Approach & What Interviewers Look For When asked to architect data fetching and caching for a complex application with multiple interacting data domains, interviewers are evaluating: Staleness Policy: Can you define when cached data becomes stale and needs refreshing? Cache Invalidation Strategy: Do you understand the hard problems of cache invalidation and have strategies to handle it? Handling Waterfalls and Concurrency: Can you prevent sequential API calls and optimize parallel fetching? Observability for API Failures: How do you monitor, track, and debug API failures in production? Retry/Backoff Policies: Do you implement resilient systems that gracefully handle transient failures? Correctness Under Distributed Conditions: Can you reason about race conditions, eventual consistency, and data integrity? Pro Tip: Staff engineers must think beyond basic caching. Focus on distributed system challenges, data consistency, and building observable, resilient systems at scale. Clarifying Questions (First 5 minutes) Before diving in, ask these questions to scope the problem: Data Domain Complexity: "How many distinct data domains are we dealing with? (e.g., user, products, orders, inventory, reviews)" "What are the relationships between domains? Do they depend on each other?" "Are there any eventually consistent domains (e.g., analytics, recommendations)?" "What's the read:write ratio for each domain?" Scale & Performance: "How many concurrent users? 10k? 1M? 10M?" "What's the target p99 latency for data fetching? <100ms? <500ms?" "What's the data size per domain? KB? MB? GB?" "What's the acceptable staleness for each domain? Real-time? Minutes? Hours?" Technical Constraints: "Do we have control over the backend APIs, or are they third-party?" "Are the APIs RESTful, GraphQL, gRPC, or mixed?" "Do w...