Quiz

2667 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 areas2667 Architecture Fundamentals81 Distributed Systems101 Data Architecture90 Cloud Architecture87 Networking86 API & Integration Architecture78 Reliability & Resilience88 Observability81 Performance & Capacity Engineering90 Security Architecture95 Cost Architecture & FinOps92 Business Architecture93 Architecture Communication91 Enterprise Architecture91 Legacy Modernization92 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.

Quiz

What happens when a globally distributed real-time communication service loses an entire region - and how should DNS, health checks, traffic steering, failover, connection draining and data consistency interact?

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?

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?

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?

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.

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?

A leader-based coordination service loses contact with its followers while the leader itself remains healthy and continues serving. What failure modes emerge, and what prevents split-brain?

A leader-based database cluster loses network connectivity between the leader and its followers, but the leader is still running and still accepting writes from application servers that can reach it. What happens, and how does correct leader election prevent it?

A nightly job occasionally runs twice, producing duplicate charges. The team proposes a distributed lock. What do you say?

A team designs active-active across two regions with automatic failover based on health checks. What is wrong?

Your cluster fails over spuriously under load, but a real leader failure takes 45 seconds to detect. How do you resolve the tension?

Your company runs two data centres and wants automatic database failover between them. What is missing?