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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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2,721 challenges matching your filters
- Multiple ChoiceIntermediate
[Testing] Triangulation Red-Green-Refactor
qatestingtestingqa - Multiple ChoiceIntermediate
[TypeScript] Identity Type parameters
qatypescripttypescriptqa - Multiple ChoiceIntermediate
[TypeScript] Constraints Type parameters
qatypescripttypescriptqa - Multiple ChoiceIntermediate
[TypeScript] Defaults Type parameters
qatypescripttypescriptqa - Multiple ChoiceIntermediate
[TypeScript] Multiple Type parameters
qatypescripttypescriptqa - Multiple ChoiceIntermediate
[TypeScript] Conditional Type parameters
qatypescripttypescriptqa - Multiple ChoiceIntermediate
[TypeScript] Union | Type combinators
qatypescripttypescriptqa - Multiple ChoiceIntermediate
[TypeScript] Intersection & Type combinators
qatypescripttypescriptqa - Multiple ChoiceIntermediate
[TypeScript] Discriminated union Type combinators
qatypescripttypescriptqa - Multiple ChoiceIntermediate
[TypeScript] Never Type combinators
qatypescripttypescriptqa - Multiple ChoiceIntermediate
[TypeScript] Exhaustive Type combinators
qatypescripttypescriptqa - 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 - Code AnalysisIntermediate
Retry storm without backoff
system-designavailabilityretry - Code AnalysisIntermediate
Implicit type cast kills index
system-designdatabasesindexes - Code AnalysisIntermediate
Offset pagination instability
system-designapi-designpagination - Code AnalysisIntermediate
Double-charge on retry
system-designidempotencyapi-design - Code AnalysisIntermediate
Consumer without dedup
system-designmessagingidempotency - Code AnalysisIntermediate
Local rate limiter drift
system-designrate-limitingdistributed - Code AnalysisIntermediate
Full table lock from a long transaction
system-designdatabasesconcurrency - Code AnalysisIntermediate
Unbounded in-memory queue
system-designmessagingbackpressure - Code AnalysisIntermediate
Health check that lies
system-designhealth-checks - Code AnalysisIntermediate
2PC coordinator down
system-designdistributed-transactions2pc - Code AnalysisIntermediate
Exactly-once assumption in consumer
system-designmessagingsqsidempotency - Code AnalysisIntermediate
Cache eviction thrash
system-designcachingeviction - Code AnalysisIntermediate
Hot key in a cache cluster
system-designcachinghot-partition - Code AnalysisIntermediate
Consistent hashing with few vnodes
system-designconsistent-hashingload-balancing - Code AnalysisIntermediate
Deadlock from lock ordering
system-designdatabasesconcurrency - Code AnalysisIntermediate
Read-through stampede on cold start
system-designcachingstampede - Code AnalysisIntermediate
Selective column over-fetch
system-designdatabasesperformance - Code AnalysisIntermediate
Negative caching with wrong TTL
system-designcachingttl - Code AnalysisIntermediate
Double-write to cache and DB
system-designcachingcache-invalidation - Code AnalysisIntermediate
Queue with no DLQ and infinite retry
system-designmessagingdlq - Code AnalysisIntermediate
Fire-and-forget event loss
system-designmessagingoutbox - Code AnalysisIntermediate
Thundering herd from synchronized cron
system-designcachingstampede - Code AnalysisIntermediate
Cache write without invalidation on update
system-designcachingcache-invalidation - Code AnalysisIntermediate
In-memory session per instance
system-designscalabilitystateless - Code AnalysisIntermediate
Sync call in an async event loop
system-designscalabilityconcurrency - Code AnalysisIntermediate
Chatty microservice call
system-designmicroservicesperformance - Code AnalysisIntermediate
TTL jitter to prevent avalanche
cachingavalanchettl-jitter - Code AnalysisIntermediate
Connection pool exhaustion from leaked connections
connection-poolresource-leakreliability - Code AnalysisIntermediate
Unbounded cardinality metric label
metricscardinalityobservability - Code AnalysisIntermediate
Non-idempotent retry double charge
paymentsidempotencyretry - Code AnalysisIntermediate
Unbounded queue without maxsize
backpressurequeuememory - Code AnalysisIntermediate
Quorum write to minority partition
quorumpartitioncap - Code AnalysisIntermediate
Write to a read replica
replicationread-replicarouting - Code AnalysisIntermediate
Outbox relay skipped without ordering
outboxcdcordering - Code AnalysisIntermediate
Idempotent receiver dedupe check
idempotencyat-least-oncededupe - Code AnalysisIntermediate
Outbox pattern race condition
outboxexactly-oncerelay - Code AnalysisIntermediate
Kafka transaction + sink exactly-once
kafkaexactly-oncetransactions - Code AnalysisIntermediate
Redis distributed lock expiry race
distributed-lockredisfencing - Code AnalysisIntermediate
Circuit breaker half-open bug
circuit-breakerresiliencehalf-open
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