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2948 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 areas2948 Architecture Fundamentals91 Distributed Systems101 Data Architecture90 Cloud Architecture87 Networking96 API & Integration Architecture87 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 Parallel Run.

  1. Parallel Run advanced

    A financial calculation engine is being replaced and the results must be proven equivalent before cutover. How should a parallel run be designed, and how are discrepancies triaged?

    3 min answer parallel-runmigrationreconciliationfinance
  2. Parallel Run advanced

    A general ledger replacement runs in parallel for five months. The nightly comparison checks daily totals per account class and they match to the penny every single night. Three weeks after cutover, finance finds that about 900 customers have had interest posted to the wrong account class since month two, and the daily totals were always correct. What failed, and which design decision made it possible?

    3 min answer parallel runreconciliationaggregatesgeneral ledger
  3. Parallel Run advanced

    A logistics platform is replacing its core routing system. Should it run the old and new systems in parallel, and for how long?

    2 min answer delhiveryparallel-runverificationcutover
  4. Parallel Run intermediate

    An enterprise runs old and new systems in parallel to validate the replacement. What makes a parallel run effective, and what makes it expensive theatre?

    2 min answer parallel-runverificationcomparisoncutover
  5. Parallel Run advanced

    You are reimplementing a legacy capability. What does running old and new in parallel find that testing cannot?

    2 min answer parallel-runlegacyundocumented-behaviourtriage