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Aporeon

Technical interview practice, from one developer to another.

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Backend System Design Foundation

Data & APIs

API/data boundaries, contracts, versioning, idempotency, and request/response design.

33 drillsPractice one at a timeOrdered pathConcept questionComparison questionArchitecture scenarioSystem design

Recommended start

Request Pipeline

Explains how an HTTP request flows through ASP.NET Core middleware, routing, endpoint execution, and response generation.

Easy~5 minStep 1 of 33

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33 of 33 shown

1Request PipelineRecommended startExplains how an HTTP request flows through ASP.NET Core middleware, routing, endpoint execution, and response generation.Concept questionEasy~5 min.NETASP.NET CoreC#Practice 2Routing & EndpointsExplains endpoint routing, route templates, HTTP method matching, endpoint metadata, and ambiguity problems.Concept questionMedium~7 min.NETASP.NET CoreC#Practice 3ProblemDetails vs Custom ErrorsUses RFC 9457 Problem Details as a stable, safe error contract with documented problem types, actionable extensions, and centralized ASP.NET mapping.Comparison questionMedium~7 min.NETASP.NET CoreC#Practice 4Route vs Query vs BodyPlaces identity, optional selection controls, command representations, headers, and files in predictable HTTP locations while accounting for security, caching, limits, and model binding.Comparison questionMedium~7 min.NETASP.NET CoreC#Practice 5Request DTOsDesign request DTOs that protect API contracts from domain and persistence models.Architecture scenarioMedium~10 min.NETASP.NET CoreC#Practice 6Validation StrategyPlaces contract, use-case, domain, authorization, and database validation at the boundaries that can enforce each rule consistently.Architecture scenarioMedium~10 min.NETASP.NET CoreC#Practice 7Pagination & FilteringDesign list endpoints with pagination, filtering, sorting, limits, and database-aware performance behavior.Architecture scenarioMedium~10 min.NETASP.NET CoreC#Practice 8API VersioningIntroduces API versions only for unavoidable breaks, with explicit routing, versioned documentation, migration support, telemetry, deprecation, and removal criteria.Architecture scenarioMedium~10 min.NETASP.NET CoreC#Practice 9OpenAPI ContractUse OpenAPI for API design, client integration, testing, and contract review in ASP.NET Core services.Architecture scenarioMedium~10 min.NETASP.NET CoreC#Practice 10SQL JoinsExplains SQL joins for API response shapes with practical .NET data-access examples and production trade-offs.Concept questionMedium~7 min.NETC#EF CorePractice 11Indexes for APIsConnects API query shape to index order, selectivity, execution plans, write cost, and safe production rollout.Concept questionMedium~7 min.NETC#EF CorePractice 12API CompatibilityBuilds request and response contracts that tolerate independently deployed clients through explicit ownership, additive evolution, stable semantics, and measured deprecation.Architecture scenarioHard~12 min.NETASP.NET CoreC#Practice 13Security BoundariesSeparates identity issuance, untrusted client behavior, API authorization, tenant isolation, resource checks, and token-handling responsibilities.System designHard~20 min.NETASP.NET CoreC#Practice 14Composite IndexesExplains composite index column order with practical .NET data-access examples and production trade-offs.Concept questionHard~9 min.NETC#EF CorePractice 15Public vs Internal APIsCompare public and internal APIs in terms of compatibility, documentation, security, support, and evolution speed.Architecture scenarioMedium~10 min.NETASP.NET CoreC#Practice 16Offset vs CursorExplains offset versus cursor pagination with practical .NET data-access examples and production trade-offs.Comparison questionHard~9 min.NETC#EF CorePractice 17Error Handling StrategyDesign API error handling across validation errors, conflicts, auth failures, not-found responses, and unexpected exceptions.Architecture scenarioHard~12 min.NETASP.NET CoreC#Practice 18API ConsistencyExplain API behavior when data and operations cross services with separate data ownership.System designHard~20 min.NETASP.NET CoreC#Practice 19Breaking API ChangeReviews a proposed response-field rename by finding consumers, classifying the break, choosing a migration path, and proving rollout and removal are safe.Code reviewHard~12 min.NETASP.NET CoreC#Practice 20Optimistic ConcurrencyDesigns an EF Core optimistic-concurrency contract around tokens, conflict policy, HTTP semantics, merge behavior, and real relational tests.Concept questionHard~9 min.NETC#EF CorePractice 21Safe MigrationsExplains safe EF Core migrations with practical .NET data-access examples and production trade-offs.Architecture scenarioHard~12 min.NETC#EF CorePractice 22Avoid EF EntitiesExplains returning EF entities from APIs with practical .NET data-access examples and production trade-offs.Concept questionEasy~5 min.NETC#EF CorePractice 23Raw SQL RiskExplains raw SQL in EF Core with practical .NET data-access examples and production trade-offs.Concept questionMedium~7 min.NETC#EF CorePractice 24Filter InjectionExplains dynamic filters and SQL injection risk with practical .NET data-access examples and production trade-offs.Debugging scenarioHard~12 min.NETC#EF CorePractice 25Soft DeleteExplains soft delete in EF Core APIs with practical .NET data-access examples and production trade-offs.Architecture scenarioMedium~10 min.NETC#EF CorePractice 26Tenant FilteringExplains multi-tenant data filtering with practical .NET data-access examples and production trade-offs.Architecture scenarioHard~12 min.NETC#EF CorePractice 27Constraints vs ValidationExplains database constraints versus application validation with practical .NET data-access examples and production trade-offs.Comparison questionMedium~7 min.NETC#EF CorePractice 28Read ModelsExplains read models for complex API screens with practical .NET data-access examples and production trade-offs.Architecture scenarioHard~12 min.NETC#EF CorePractice 29Filtered IncludeExplains filtered Include in EF Core with practical .NET data-access examples and production trade-offs.Concept questionMedium~7 min.NETC#EF CorePractice 30Global Query FiltersExplains global query filters in EF Core with practical .NET data-access examples and production trade-offs.Concept questionMedium~7 min.NETC#EF CorePractice 31Owned entities and complex typesChooses between EF Core complex types, owned entities, and regular entities from value semantics, identity, ownership, querying, and storage needs.Concept questionMedium~7 min.NETC#EF CorePractice 32Shadow PropertiesExplains EF Core shadow properties for audit or infrastructure columns with practical .NET data-access examples and production trade-offs.Concept questionMedium~7 min.NETC#EF CorePractice 33Streaming DataCovers large exports, uploads, and API responses where bounded memory matters more than convenience.Architecture scenarioMedium~10 min.NETASP.NET CoreC#Practice

Practice order

33 drillsOne at a time

1Request PipelineUp next / Easy / ~5 min
2Routing & EndpointsMedium / ~7 min
3ProblemDetails vs Custom ErrorsMedium / ~7 min
4Route vs Query vs BodyMedium / ~7 min
5Request DTOsMedium / ~10 min
6Validation StrategyMedium / ~10 min
7Pagination & FilteringMedium / ~10 min
8API VersioningMedium / ~10 min

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