Challenge Library
Coding Challenges
5,893 curated questions across every arena — browse by topic, then jump into a live 3-minute battle to put them to the test.
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60 challenges matching your filters
Clear topic filter- Multiple ChoiceIntermediate
Virtual nodes in consistent hashing
system-designconsistent-hashing - Multiple ChoiceIntermediate
TTL jitter
system-designcaching - Multiple ChoiceIntermediate
CDN invalidation tradeoff
system-designcdncache-invalidation - Multiple ChoiceIntermediate
Read-your-writes consistency
system-designconsistencyreplication - Multiple ChoiceIntermediate
PACELC extension
system-designpacelccap-theorem - Multiple ChoiceIntermediate
Serializable vs linearizable
system-designconsistency - Multiple ChoiceIntermediate
Exactly-once reality
system-designmessagingkafka - Multiple ChoiceIntermediate
Idempotency key design
system-designapi-designidempotency - Multiple ChoiceIntermediate
Backpressure
system-designmessagingbackpressure - Multiple ChoiceIntermediate
Distributed rate limiting accuracy
system-designrate-limitingdistributed - Multiple ChoiceIntermediate
Sliding window vs fixed window
system-designrate-limiting - Multiple ChoiceIntermediate
gRPC vs REST
system-designapi-designgrpc - Multiple ChoiceIntermediate
Saga pattern compensation
system-designdistributed-transactionssaga - Multiple ChoiceIntermediate
Outbox pattern
system-designdistributed-transactionsoutbox - Multiple ChoiceIntermediate
Availability math
system-designavailability - Multiple ChoiceIntermediate
Circuit breaker states
system-designavailabilitycircuit-breaker - Multiple ChoiceIntermediate
Pre-signed URLs
system-designstorages3 - Multiple ChoiceIntermediate
WebSocket vs long polling
system-designreal-timewebsockets - Multiple ChoiceIntermediate
Elasticsearch refresh vs commit
system-designsearchelasticsearch - Multiple ChoiceIntermediate
Clock skew and Snowflake
system-designunique-idsnowflake - Multiple ChoiceIntermediate
Microservices vs monolith
system-designmicroservices - Multiple ChoiceIntermediate
Capacity estimation: peak vs average
system-designcapacity-estimation - Multiple ChoiceIntermediate
Read-heavy vs write-heavy design
system-designcapacity-estimationdatabases - Multiple ChoiceIntermediate
Hot partition in Kafka
system-designmessagingkafkasharding - Multiple ChoiceIntermediate
RabbitMQ vs Kafka model
system-designmessagingkafkarabbitmq - Multiple ChoiceIntermediate
Thundering herd on cache key deletion
system-designcachingstampede - Multiple ChoiceIntermediate
Bloom filter pre-check
system-designcachingbloom-filter - Multiple ChoiceIntermediate
Split-brain
system-designconsensusavailability - Multiple ChoiceIntermediate
Fencing tokens
system-designconsensusleader-election - Multiple ChoiceIntermediate
Outbox relay ordering
system-designoutboxmessaging - Multiple ChoiceIntermediate
Metrics cardinality explosion
system-designobservabilitymetrics - Multiple ChoiceIntermediate
Exponential backoff with jitter
system-designavailabilityretry - Multiple ChoiceIntermediate
Idempotency store TTL
system-designidempotencyapi-design - Multiple ChoiceIntermediate
Read-through cache
system-designcaching - 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
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