Portfolio ↗

Quiz

2627 questions of the kind that actually get asked — in interviews, in architecture review boards, and by the person who has to run the thing at 3 AM. Every answer states the trade-off rather than the slogan, and says when the obvious choice is the wrong one.

All areas2627 Architecture Fundamentals81 Distributed Systems101 Data Architecture90 Cloud Architecture77 Networking86 API & Integration Architecture78 Reliability & Resilience88 Observability81 Performance & Capacity Engineering90 Security Architecture85 Cost Architecture & FinOps82 Business Architecture93 Architecture Communication91 Enterprise Architecture91 Legacy Modernization82 AI-Era Architecture86 Software Architecture & Engineering84 Architecture Patterns84 Architecture Decision-Making91 The Architect's Meta-Skills92 Delivery & Release Engineering93 Platform Engineering & Developer Experience92 Testing & Quality Architecture90 Data Platform Architecture88 Streaming & Real-Time Data93 Data Governance & Semantics81 Frontend & Experience Architecture91 Edge, Mobile & IoT88 Regulatory & Data Protection Architecture90 Assurance, Audit & Model Risk88
Difficulty Any beginner intermediate advanced

53 questions in Performance & Capacity.

  1. Concurrency advanced Multiple choice

    Why is limiting concurrency more effective than limiting request rate when protecting a service?

    2 min answer concurrencyrate-limitinglittles-lawprotection
  2. Connection Pooling advanced

    A service under load has high latency and low CPU. The team increases the database connection pool and it gets worse. Why?

    2 min answer sharechatconnection-poolcontentionqueueing
  3. Database Performance advanced

    A multi-tenant platform's database performance is fine for most tenants and severely degraded for a few. What are the likely causes and their fixes?

    2 min answer database-performancemulti-tenancystatisticsplans
  4. Database Performance advanced

    A query that ran in 40 ms has taken 40 seconds since Tuesday. The query and the code are unchanged. What happened?

    2 min answer databasequery-planstatisticsdiagnosis
  5. Database Performance advanced

    A search product must choose between indexing throughput and query latency on the same hardware. How should the trade be made explicit and managed?

    2 min answer meilisearchsearchindexingcontention
  6. Database Performance advanced

    A voucher-redemption feature creates a single hot row that thousands of buyers hit in the same second. Compare row-level locking, optimistic concurrency, bucketed counters and an in-memory reservation service.

    3 min answer hot-rowcontentionoptimistic-concurrencyreservation
  7. Database Performance advanced

    An application with ten million users has a database bottleneck. In what order do you intervene, and why is sharding last?

    2 min answer databasescalingshardingreplicas
  8. Database Performance advanced

    Review this proposal. A team has six slow queries against a 400 GB table taking 40,000 writes a minute, and proposes adding six indexes, one per query. What would you remove, what would you change, and what would you keep?

    3 min answer indexeswrite amplificationbuffer poolquery plans
  9. Horizontal vs Vertical Scaling advanced

    A stateful service runs on 16 large nodes, each holding a large in-memory working set. You must move to 200 small nodes under live traffic, for finer failure granularity and better bin-packing. Sequence the migration, and say what changes that nobody plans for.

    3 min answer scalingpartitioningcache hit ratefan-out
  10. Latency advanced

    A collaborative editor must feel instantaneous to users on different continents, where physics imposes a floor of roughly 150 ms round trip. How is the latency requirement met at all?

    2 min answer latencylocal-firstoptimistic-uiperception
  11. Latency advanced

    A load generator reports a p99 of 30 ms at 5,000 rps. In production at the same rate, users report multi-second stalls, and the service's own latency metrics agree with the load test. Both measurements are honest. What is being missed?

    3 min answer coordinated omissionload testingpercentilesqueueing
  12. Latency advanced

    A page makes 20 parallel backend calls, each with a p99 of 1 second and a p50 of 40 ms. What is the page's latency profile?

    2 min answer latencytailfanoutpercentiles