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2988 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 areas2988 Architecture Fundamentals91 Distributed Systems111 Data Architecture100 Cloud Architecture97 Networking96 API & Integration Architecture97 Reliability & Resilience99 Observability92 Performance & Capacity Engineering100 Security Architecture105 Cost Architecture & FinOps102 Business Architecture103 Architecture Communication102 Enterprise Architecture100 Legacy Modernization102 AI-Era Architecture106 Software Architecture & Engineering93 Architecture Patterns94 Architecture Decision-Making101 The Architect's Meta-Skills102 Delivery & Release Engineering103 Platform Engineering & Developer Experience102 Testing & Quality Architecture102 Data Platform Architecture98 Streaming & Real-Time Data103 Data Governance & Semantics91 Frontend & Experience Architecture101 Edge, Mobile & IoT98 Regulatory & Data Protection Architecture99 Assurance, Audit & Model Risk98
Difficulty Any beginner intermediate advanced

5 questions in Idempotency.

  1. Idempotency advanced Multiple choice

    A billing platform sends a webhook, the customer's endpoint times out, and the customer's system retries the operation several times. How should idempotency keys, durable event state, delivery attempts, ordering and reconciliation prevent duplicate billing?

    2 min answer chargebeewebhooksidempotencyat-least-once
  2. Idempotency intermediate Multiple choice

    A marketplace checkout calls a payment API. Mobile clients on poor networks time out and retry, and some customers are charged twice. Where exactly must the deduplication record be written for this to be fixed?

    2 min answer idempotencyretriespaymentscorrectness
  3. Idempotency advanced

    A payments API receives the same charge request twice because a mobile client retried after a timeout. How should idempotency keys be scoped, stored, expired and validated, and what happens when the first attempt is still in flight?

    2 min answer stripeidempotencyretriespayments
  4. Idempotency advanced

    An API platform sends messages on behalf of external developers whose clients retry aggressively after network timeouts. Design idempotency so that a retried request never sends a second message - and state precisely where the guarantee begins and ends.

    2 min answer idempotencyretriesapi-designtwilio
  5. Idempotency advanced Multiple choice

    Mobile clients on poor networks retry payment requests after timeouts. Where must idempotency be enforced, what must be durable before responding, and what is the most common scoping mistake?

    2 min answer phonepeidempotencyretriesmobile