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Aporeon

Technical interview practice, from one developer to another.

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Data Performance & Operations

Indexes, generated SQL, diagnostics, timeouts, cancellation, connection pressure, migrations, bulk imports, and production investigations.

14 drillsPractice one at a timeOrdered pathConcept questionArchitecture scenarioDebugging scenario

Recommended start

Indexes for APIs

Connects API query shape to index order, selectivity, execution plans, write cost, and safe production rollout.

Medium~7 minStep 1 of 14

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1Indexes for APIsRecommended startConnects API query shape to index order, selectivity, execution plans, write cost, and safe production rollout.Concept questionMedium~7 min.NETC#EF CorePractice 2Composite IndexesExplains composite index column order with practical .NET data-access examples and production trade-offs.Concept questionHard~9 min.NETC#EF CorePractice 3Safe MigrationsExplains safe EF Core migrations with practical .NET data-access examples and production trade-offs.Architecture scenarioHard~12 min.NETC#EF CorePractice 4EF Core RetriesExplains EF Core connection resiliency and retries with practical .NET data-access examples and production trade-offs.Concept questionHard~9 min.NETC#EF CorePractice 5EF Query DiagnosticsExplains EF Core query performance diagnostics with practical .NET data-access examples and production trade-offs.Debugging scenarioHard~12 min.NETC#EF CorePractice 6Query TagsExplains how query tags, request correlation, and telemetry help connect slow SQL back to code paths.Debugging scenarioMedium~10 min.NETApplication InsightsASP.NET CorePractice 7High DB CPUExplains high database CPU after an API change with practical .NET data-access examples and production trade-offs.Debugging scenarioHard~12 min.NETC#EF CorePractice 8Connection Pool ExhaustionExplains database connection pool exhaustion with practical .NET data-access examples and production trade-offs.Debugging scenarioHard~12 min.NETC#EF CorePractice 9EF Core CancellationExplain why request cancellation should flow into EF Core queries and where it does or does not help.Architecture scenarioMedium~10 min.NETASP.NET CoreC#Practice 10Query TimeoutsFits database command timeouts into endpoint latency budgets while diagnosing slow SQL, blocking, pool pressure, and uncertain write outcomes.Concept questionMedium~7 min.NETC#EF CorePractice 11Batch ImportExplains batching, tracking control, idempotency, validation, and operational safety for large EF Core imports.Architecture scenarioHard~12 min.NETASP.NET CoreEF CorePractice 12Migration ReviewReviews and stages destructive EF Core schema changes around live data, locks, mixed application versions, recovery, and rollback.Debugging scenarioHard~12 min.NETASP.NET CoreEF CorePractice 13Slow EF QueryInvestigates a growing-data EF Core slowdown through one correlated request, generated SQL, representative parameters, execution plan, waits, query shape, measured repair, and guarded rollout.Debugging scenarioHard~12 min.NETApplication InsightsASP.NET CorePractice 14Connection pool exhaustionExplains physical connection reuse, pool partitioning, short ownership, exhaustion causes, diagnostics, and why increasing the pool is not the first fix.Concept questionMedium~7 min.NETSQL ServerPractice

Practice order

14 drillsOne at a time

1Indexes for APIsUp next / Medium / ~7 min
2Composite IndexesHard / ~9 min
3Safe MigrationsHard / ~12 min
4EF Core RetriesHard / ~9 min
5EF Query DiagnosticsHard / ~12 min
6Query TagsMedium / ~10 min
7High DB CPUHard / ~12 min
8Connection Pool ExhaustionHard / ~12 min

+6 more drills in this section