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
[TypeScript] Record<K,V> Built-in type transforms
qatypescripttypescriptqa - Multiple ChoiceHard
[Webpack] Dynamic import Lazy load parts of app
qawebpackwebpackqa - Multiple ChoiceHard
[Webpack] SplitChunks Lazy load parts of app
qawebpackwebpackqa - Multiple ChoiceHard
[Webpack] Vendor bundle Lazy load parts of app
qawebpackwebpackqa - Multiple ChoiceHard
[Webpack] Prefetch Lazy load parts of app
qawebpackwebpackqa - Multiple ChoiceHard
[Webpack] Lazy routes Lazy load parts of app
qawebpackwebpackqa - Multiple ChoiceBeginner
[Webpack] devServer Development experience
qawebpackwebpackqa - Multiple ChoiceBeginner
[Webpack] Proxy Development experience
qawebpackwebpackqa - Multiple ChoiceBeginner
[Webpack] HMR Development experience
qawebpackwebpackqa - Multiple ChoiceBeginner
[Webpack] Host/port Development experience
qawebpackwebpackqa - Multiple ChoiceBeginner
[Webpack] Watch Development experience
qawebpackwebpackqa - Multiple ChoiceBeginner
[Webpack] Entry Define build start and end
qawebpackwebpackqa - Multiple ChoiceBeginner
[Webpack] Output Define build start and end
qawebpackwebpackqa - Multiple ChoiceBeginner
[Webpack] Multiple entries Define build start and end
qawebpackwebpackqa - Multiple ChoiceBeginner
[Webpack] PublicPath Define build start and end
qawebpackwebpackqa - Multiple ChoiceBeginner
[Webpack] Hash in filename Define build start and end
qawebpackwebpackqa - Multiple ChoiceIntermediate
[Webpack] Babel Transform non-JS files
qawebpackwebpackqa - Multiple ChoiceIntermediate
[Webpack] CSS Transform non-JS files
qawebpackwebpackqa - Multiple ChoiceIntermediate
[Webpack] File loader Transform non-JS files
qawebpackwebpackqa - Multiple ChoiceIntermediate
[Webpack] TypeScript Transform non-JS files
qawebpackwebpackqa - Multiple ChoiceIntermediate
[Webpack] Sass Transform non-JS files
qawebpackwebpackqa - Multiple ChoiceIntermediate
[Webpack] HtmlWebpackPlugin Bundle-wide operations
qawebpackwebpackqa - Multiple ChoiceIntermediate
[Webpack] MiniCssExtract Bundle-wide operations
qawebpackwebpackqa - Multiple ChoiceIntermediate
[Webpack] DefinePlugin Bundle-wide operations
qawebpackwebpackqa - Multiple ChoiceIntermediate
[Webpack] TerserPlugin Bundle-wide operations
qawebpackwebpackqa - Multiple ChoiceIntermediate
[Webpack] HotModuleReplacement Bundle-wide operations
qawebpackwebpackqa - Multiple ChoiceHard
[Webpack] ESM required Remove unused exports
qawebpackwebpackqa - Multiple ChoiceHard
[Webpack] Side effects flag Remove unused exports
qawebpackwebpackqa - Multiple ChoiceHard
[Webpack] Production mode Remove unused exports
qawebpackwebpackqa - Multiple ChoiceHard
[Webpack] CommonJS Remove unused exports
qawebpackwebpackqa - Multiple ChoiceHard
[Webpack] Lodash Remove unused exports
qawebpackwebpackqa - Code AnalysisHard
N+1 query in an ORM loop
system-designdatabasesn-plus-one - Code AnalysisHard
Cache stampede on expiry
system-designcachingstampede - Code AnalysisIntermediate
Retry storm without backoff
system-designavailabilityretry - Code AnalysisHard
Read-modify-write lost update
system-designconcurrencydatabases - Code AnalysisHard
Hot shard from a skewed key
system-designshardinghot-partition - Code AnalysisBeginner
NULL comparison bug
system-designdatabasessql - Code AnalysisIntermediate
Implicit type cast kills index
system-designdatabasesindexes - Code AnalysisIntermediate
Offset pagination instability
system-designapi-designpagination - Code AnalysisBeginner
Unbounded SELECT without index
system-designdatabasesindexesreplication - Code AnalysisIntermediate
Double-charge on retry
system-designidempotencyapi-design - Code AnalysisHard
Sync replication availability trap
system-designreplicationcap-theorem - Code AnalysisIntermediate
Consumer without dedup
system-designmessagingidempotency - Code AnalysisIntermediate
Local rate limiter drift
system-designrate-limitingdistributed - Code AnalysisBeginner
Missing index on a foreign-key join
system-designdatabasesindexes - Code AnalysisHard
Fan-out-on-write celebrity
system-designnews-feedfan-out - Code AnalysisIntermediate
Full table lock from a long transaction
system-designdatabasesconcurrency - Code AnalysisHard
Split-brain from naive failover
system-designconsensusavailability - Code AnalysisIntermediate
Unbounded in-memory queue
system-designmessagingbackpressure - Code AnalysisBeginner
Cache key without entity version
system-designcachingcache-invalidation - Code AnalysisBeginner
Thundering herd on connection pool resize
system-designdatabasesconnection-pool - Code AnalysisIntermediate
Health check that lies
system-designhealth-checks - Code AnalysisBeginner
Read replica lag on user update
system-designreplicationconsistency - Code AnalysisHard
Outbox without proper relay
system-designoutboxdistributed-transactions - Code AnalysisIntermediate
2PC coordinator down
system-designdistributed-transactions2pc - Code AnalysisHard
Thundering herd with negative result
system-designcachingcache-penetration - Code AnalysisIntermediate
Exactly-once assumption in consumer
system-designmessagingsqsidempotency - Code AnalysisHard
Unbounded cardinality metric
system-designobservabilitymetrics - Code AnalysisIntermediate
Cache eviction thrash
system-designcachingeviction - Code AnalysisHard
CAS retry livelock
system-designconcurrencydistributed-counter
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