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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 Coexistence Patterns.

  1. Coexistence Patterns advanced

    A migration will take eighteen months, during which old and new systems both serve production. How should the coexistence period be designed?

    2 min answer digitcoexistenceroutingconsistency
  2. Coexistence Patterns advanced

    During a multi-year migration, old and new systems must coexist. Which coexistence patterns are sustainable and which accumulate debt?

    2 min answer coexistencedual-writeownershipreconciliation
  3. Coexistence Patterns advanced

    Eighteen months into a coexistence period, customer records are authoritative in the new system and order records are still authoritative in the old one. A refund credits the customer and cancels the order line. What happens the first time the credit commits and the cancellation is rejected?

    3 min answer coexistencewrite ownershipsagascompensation
  4. Coexistence Patterns advanced

    Old and new stores both hold 42 million customer records during a coexistence period. The nightly full-row comparison now takes 6 hours 40 minutes against a 4-hour window, and the legacy side serves the export at about 1800 rows per second. Roughly what does a hash-bucket comparison cost instead, and which assumption decides whether it fits?

    3 min answer coexistence-patternsreconciliationmerklehashing
  5. Coexistence Patterns advanced

    Your cutover plan says switch reads, then switch writes, then decommission. A reviewer asks what happens at 02:00 if the new store turns out to be wrong after writes have moved. What mechanism makes the write switch reversible, and what is the honest unavailability window?

    3 min answer youtubevitesscutoverreverse-replication