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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150 challenges matching your filters
Clear topic filter- Multiple ChoiceIntermediate
Capacity estimation: peak vs average
system-designcapacity-estimation - Multiple ChoiceBeginner
Storage sizing with replication
system-designcapacity-estimationstorage - Multiple ChoiceBeginner
Bandwidth estimation
system-designcapacity-estimationbandwidth - Multiple ChoiceIntermediate
Read-heavy vs write-heavy design
system-designcapacity-estimationdatabases - Multiple ChoiceHard
Little's Law for concurrency
system-designcapacity-estimationlatency - Multiple ChoiceIntermediate
Hot partition in Kafka
system-designmessagingkafkasharding - Multiple ChoiceHard
Kafka consumer group rebalance
system-designmessagingkafka - Multiple ChoiceIntermediate
RabbitMQ vs Kafka model
system-designmessagingkafkarabbitmq - Multiple ChoiceBeginner
SQS visibility timeout
system-designmessagingsqs - Multiple ChoiceHard
Visibility timeout too short
system-designmessagingsqsidempotency - Multiple ChoiceIntermediate
Thundering herd on cache key deletion
system-designcachingstampede - Multiple ChoiceBeginner
Cache warming
system-designcaching - Multiple ChoiceIntermediate
Bloom filter pre-check
system-designcachingbloom-filter - Multiple ChoiceBeginner
Idempotent HTTP methods
system-designapi-designidempotency - Multiple ChoiceHard
Lost update race
system-designconcurrencyconsistency - Multiple ChoiceHard
Optimistic vs pessimistic locking
system-designconcurrencydatabases - Multiple ChoiceIntermediate
Split-brain
system-designconsensusavailability - Multiple ChoiceIntermediate
Fencing tokens
system-designconsensusleader-election - Multiple ChoiceIntermediate
Outbox relay ordering
system-designoutboxmessaging - Multiple ChoiceBeginner
Distributed tracing purpose
system-designobservabilitytracing - Multiple ChoiceHard
Tail-based sampling
system-designobservabilitytracing - Multiple ChoiceIntermediate
Metrics cardinality explosion
system-designobservabilitymetrics - Multiple ChoiceIntermediate
Exponential backoff with jitter
system-designavailabilityretry - Multiple ChoiceHard
Retry amplification
system-designavailabilityretry - Multiple ChoiceBeginner
Failover active-passive vs active-active
system-designavailabilityfailover - Multiple ChoiceBeginner
Nines and downtime budget
system-designavailabilitynines - Multiple ChoiceIntermediate
Idempotency store TTL
system-designidempotencyapi-design - Multiple ChoiceHard
Quorum without read repair
system-designquorumconsistency - Multiple ChoiceIntermediate
Read-through cache
system-designcaching - Multiple ChoiceHard
Cache invalidation on write
system-designcachingcache-invalidation - 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 - Code AnalysisBeginner
Snowflake clock rollback
system-designunique-idsnowflake
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