Challenge Library
Coding Challenges
5,893 curated questions across every arena — browse by topic, then jump into a live 2-minute battle to put them to the test.
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5,893 challenges total
- Multiple ChoiceHard
Thundering herd on cache expiry
architectureresiliencecaching - Multiple ChoiceHard
Backpressure vs dropping
architectureresiliencebackpressure - Multiple ChoiceHard
Consistency boundary choice
architecturedddconsistency - Multiple ChoiceBeginner
Cross-cutting logging
architecturecross-cuttinglogging - Multiple ChoiceHard
Correlation ids in distributed tracing
architectureobservabilitytracing - Multiple ChoiceBeginner
Config as external concern
architectureconfigurationtwelve-factor - Multiple ChoiceBeginner
Composition over inheritance
architectureoopcomposition - Multiple ChoiceHard
Fragile base class problem
architectureoopinheritance - Multiple ChoiceHard
Aggregate size trade-off
architecturedddaggregate - Multiple ChoiceIntermediate
Event-carried state transfer vs notification
architectureedacoupling - Multiple ChoiceIntermediate
Interface versioning in events
architectureedaversioning - Multiple ChoiceHard
Modularity enforcement
architecturemodularityfitness-functions - Multiple ChoiceBeginner
Anti-corruption in practice
architecturedddacl - Multiple ChoiceHard
Domain service vs application service
architecturedddlayering - Multiple ChoiceHard
Rich model invariant
architecturedddinvariants - Multiple ChoiceIntermediate
Make illegal states unrepresentable
architecturedddtype-modeling - Multiple ChoiceBeginner
Port naming by role
architecturehexagonalnaming - Multiple ChoiceHard
Strangler routing: shadow traffic
architecturemigrationstrangler-fig - Multiple ChoiceHard
Service granularity trap
architecturemicroservicesgranularity - Multiple ChoiceIntermediate
Architecture vs design decision
architecturedecision-making - Code AnalysisBeginner
Anemic model allows invalid state
architecturedddanemic-model - Code AnalysisIntermediate
Violated LSP with strengthened precondition
architecturesolidlsp - Code AnalysisIntermediate
Circular dependency between modules
architecturemodularitydependencies - Code AnalysisIntermediate
Wrong abstraction: premature interface
architectureover-abstractiondi - Code AnalysisIntermediate
Coupling leak: vendor type in domain
architecturesoliddiphexagonal - Code AnalysisIntermediate
Observer memory leak
architecturedesign-patternsobserver - Code AnalysisBeginner
SRP: god class
architecturesolidsrp - Code AnalysisIntermediate
Unit of Work spanning aggregates
architecturedddunit-of-work - Code AnalysisIntermediate
Strategy gone wrong: enum switch
architecturesolidocp - Code AnalysisIntermediate
Eventual consistency bug after write
architecturecqrseventual-consistency - Code AnalysisIntermediate
Decorator vs subclass explosion
architecturedesign-patternsdecorator - Code AnalysisHard
Saga: non-idempotent compensation
architecturedistributedsagaidempotency - Code AnalysisIntermediate
Circuit breaker covers wrong scope
architectureresiliencecircuit-breaker - Code AnalysisHard
Dual-write inconsistency
architectureedaoutbox - Code AnalysisBeginner
LSP: equals/hashCode mismatch
architecturesolidlsp - Code AnalysisBeginner
Coupling metric read
architecturemetricscoupling - Code AnalysisIntermediate
Fitness function for layering
architecturefitness-functionshexagonal - Code AnalysisIntermediate
Repository leaking persistence
architecturedesign-patternsrepository - Code AnalysisIntermediate
Aggregate reference by object
architecturedddaggregate - Code AnalysisIntermediate
Strangler with broken routing
architecturemigrationstrangler-fig - Code AnalysisHard
Facade hides subsystem steps
architecturedesign-patternsfacade - Code AnalysisIntermediate
Wrong abstraction via forced hierarchy
architectureover-abstractionlsp - Code AnalysisBeginner
Command with undo
architecturedesign-patternscommand - Code AnalysisIntermediate
Ambassador vs Sidecar use
architecturedesign-patternssidecarambassador - Code AnalysisIntermediate
Adapter vs Facade distinction by code
architecturedesign-patternsadapter - Code AnalysisIntermediate
Bounded context language clash
architecturedddbounded-context - Code AnalysisBeginner
Feature flag stale branch
architecturefeature-flagstechnical-debt - Code AnalysisIntermediate
Backpressure ignored
architectureresiliencebackpressure - Code AnalysisBeginner
Command/query separation violation
architecturecqrsprinciples - Code AnalysisBeginner
ISP in a module interface
architecturesolidisp - Code AnalysisIntermediate
Event sourcing projection replay bug
architectureevent-sourcingprojections - Code AnalysisBeginner
CQRS lag breaks read-your-writes
architecturecqrseventual-consistency - Code AnalysisHard
Thundering herd on expiry
architectureresiliencecaching - Code AnalysisBeginner
Anemic model with validation elsewhere
architecturedddanemic-model - Code AnalysisIntermediate
LSP: widening (not narrowing) can also break
architecturesolidlsp - Code AnalysisBeginner
Dependency inversion missing in service
architecturesoliddip - Code AnalysisIntermediate
Contract regression: additive vs breaking
architectureapiversioningbackward-compatibility - Code AnalysisBeginner
Choreography observability gap
architectureedasaga - Code AnalysisIntermediate
Orchestration single point
architecturesagaresilience - Code AnalysisBeginner
Shared module creates cycle at package level
architecturemodularitydependencies
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