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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38 challenges matching your filters
Clear topic filter- Multiple ChoiceHard
Cache stampede / thundering herd
system-designcachingstampede - Multiple ChoiceHard
Probabilistic early expiration
system-designcachingstampede - Multiple ChoiceHard
Sharding key choice
system-designdatabasessharding - Multiple ChoiceHard
Quorum read/write overlap
system-designconsistencyquorum - Multiple ChoiceHard
Two-phase commit blocking
system-designdistributed-transactions2pc - Multiple ChoiceHard
Bulkhead isolation
system-designavailabilitybulkhead - Multiple ChoiceHard
Fan-out on write vs read
system-designreal-timefan-outnews-feed - Multiple ChoiceHard
Little's Law for concurrency
system-designcapacity-estimationlatency - Multiple ChoiceHard
Kafka consumer group rebalance
system-designmessagingkafka - Multiple ChoiceHard
Visibility timeout too short
system-designmessagingsqsidempotency - Multiple ChoiceHard
Lost update race
system-designconcurrencyconsistency - Multiple ChoiceHard
Optimistic vs pessimistic locking
system-designconcurrencydatabases - Multiple ChoiceHard
Tail-based sampling
system-designobservabilitytracing - Multiple ChoiceHard
Retry amplification
system-designavailabilityretry - Multiple ChoiceHard
Quorum without read repair
system-designquorumconsistency - 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 AnalysisHard
Read-modify-write lost update
system-designconcurrencydatabases - Code AnalysisHard
Hot shard from a skewed key
system-designshardinghot-partition - Code AnalysisHard
Sync replication availability trap
system-designreplicationcap-theorem - Code AnalysisHard
Fan-out-on-write celebrity
system-designnews-feedfan-out - Code AnalysisHard
Split-brain from naive failover
system-designconsensusavailability - Code AnalysisHard
Outbox without proper relay
system-designoutboxdistributed-transactions - Code AnalysisHard
Thundering herd with negative result
system-designcachingcache-penetration - Code AnalysisHard
Unbounded cardinality metric
system-designobservabilitymetrics - Code AnalysisHard
CAS retry livelock
system-designconcurrencydistributed-counter - Code AnalysisHard
Retry without idempotency on a non-idempotent path
system-designidempotencyretry - Code AnalysisHard
At-least-once with side effect before ack
system-designmessagingidempotency - Code AnalysisHard
Fencing missing on lease-based lock
system-designconsensusleader-election - Code AnalysisHard
Backpressure via unbounded broker retention
system-designmessagingbackpressure - Code AnalysisHard
Quorum read after failed write
system-designquorumconsistency - Code AnalysisHard
Idempotency key stored after the effect
system-designidempotencyconcurrency - Code AnalysisHard
Fan-out read amplification
system-designnews-feedfan-out - Code AnalysisHard
Offset commit before processing
system-designmessagingkafka - Code AnalysisHard
Unbounded retry on non-transient error
system-designresilienceretry - Code AnalysisHard
CAS without version on concurrent edit
system-designconcurrencydatabases - Code AnalysisHard
Bloom filter with no eviction
system-designcachingbloom-filter
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