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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

101 questions in Distributed Systems.

  1. CAP & PACELC advanced

    You run active-active across two regions. The link between them fails. What should each region do, and what would you have designed differently?

    2 min answer partitionquorummulti-regionavailability
  2. Circuit Breakers advanced

    A card-processing platform's downstream authorisation network is slow but not failing - responses arrive, just far too late. Why does a standard error-rate circuit breaker not help, and what does?

    2 min answer marqetacircuit-breakerlatencybrownout
  3. Circuit Breakers advanced

    A grocery platform's retailer inventory API is slow but not failing - responses take 6 seconds instead of 200 ms, and mostly succeed. Should the circuit breaker open? Analyse the trade-off.

    2 min answer circuit-breakerslatencydegradationinstacart
  4. Circuit Breakers intermediate Multiple choice

    A team proposes circuit breakers on every downstream call. What would you add, and why is the breaker not the most important control?

    2 min answer circuit-breakerbulkheadisolationfallback
  5. Circuit Breakers advanced

    After adding circuit breakers, a partial outage now lasts three times longer than it used to. What is likely happening?

    1 min answer circuit-breakerrecoveryoscillation
  6. Circuit Breakers advanced

    You maintain circuit breakers across 200 services. Configuration drift means half are misconfigured. What do you do?

    2 min answer netflixtuningscaleautomation
  7. Circuit Breakers intermediate

    Your circuit breaker opens during normal traffic spikes, causing outages it was meant to prevent. How do you configure it correctly?

    2 min answer resiliencetuningfailure
  8. Clocks & Ordering advanced

    "Interview. In a multiplayer design tool, two users move the same object at the same moment. Wall-clock timestamps disagree because their machines' clocks differ by 400 ms. How do you decide what the document should show, and what would you say to an engineer who proposes using timestamps?" What is a strong answer?

    2 min answer clocksorderingcausalitylamport
  9. Clocks & Ordering advanced

    An event-processing platform orders records by the timestamp the producing service attached. Records occasionally appear out of order and some appear to arrive before they were created. What is happening and how should ordering be established?

    2 min answer credclocksorderingcausality
  10. Clocks & Ordering advanced

    Spanner uses TrueTime — an API that returns a bounded time interval rather than a timestamp — to provide externally consistent distributed transactions. What problem does this solve, what does it cost, and when is the cost not worth paying?

    2 min answer googlespannertruetimeconsistency
  11. Clocks & Ordering advanced

    Two regions both accept writes to the same user record and resolve conflicts by last-write-wins on timestamp. Users report edits silently disappearing. Explain and fix.

    3 min answer clocksorderingconflict-resolutiondropbox
  12. Consensus Protocols advanced

    A configuration change must propagate to thousands of edge locations worldwide within seconds, while remaining safe against a bad global configuration. What consistency and rollout properties does the propagation system need?

    2 min answer consensusconfigurationedgecloudflare