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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4,318 challenges matching your filters
- Multiple ChoiceBeginner
Token bucket burst behavior
system-designrate-limiting - Multiple ChoiceIntermediate
Distributed rate limiting accuracy
system-designrate-limitingdistributed - Multiple ChoiceIntermediate
Sliding window vs fixed window
system-designrate-limiting - Multiple ChoiceBeginner
Sliding window log memory cost
system-designrate-limiting - Multiple ChoiceIntermediate
gRPC vs REST
system-designapi-designgrpc - Multiple ChoiceBeginner
Cursor vs offset pagination
system-designapi-designpagination - Multiple ChoiceBeginner
API versioning rationale
system-designapi-designversioning - Multiple ChoiceHard
Two-phase commit blocking
system-designdistributed-transactions2pc - Multiple ChoiceIntermediate
Saga pattern compensation
system-designdistributed-transactionssaga - Multiple ChoiceIntermediate
Outbox pattern
system-designdistributed-transactionsoutbox - Multiple ChoiceBeginner
SLI vs SLO vs SLA
system-designobservabilityslo - Multiple ChoiceBeginner
p99 vs mean latency
system-designobservabilitylatency - Multiple ChoiceIntermediate
Availability math
system-designavailability - Multiple ChoiceIntermediate
Circuit breaker states
system-designavailabilitycircuit-breaker - Multiple ChoiceHard
Bulkhead isolation
system-designavailabilitybulkhead - Multiple ChoiceBeginner
Blob vs object storage
system-designstorages3 - Multiple ChoiceIntermediate
Pre-signed URLs
system-designstorages3 - Multiple ChoiceIntermediate
WebSocket vs long polling
system-designreal-timewebsockets - Multiple ChoiceHard
Fan-out on write vs read
system-designreal-timefan-outnews-feed - Multiple ChoiceBeginner
Inverted index
system-designsearchinverted-index - Multiple ChoiceIntermediate
Elasticsearch refresh vs commit
system-designsearchelasticsearch - Multiple ChoiceBeginner
URL shortener key generation
system-designurl-shortenerunique-id - Multiple ChoiceBeginner
Snowflake ID structure
system-designunique-idsnowflake - Multiple ChoiceIntermediate
Clock skew and Snowflake
system-designunique-idsnowflake - Multiple ChoiceIntermediate
Microservices vs monolith
system-designmicroservices - Multiple ChoiceBeginner
Service discovery
system-designservice-discovery - Multiple ChoiceBeginner
Liveness vs readiness probe
system-designhealth-checkskubernetes - 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 - Multiple ChoiceBeginner
Back-of-envelope QPS from DAU
capacity-estimationqpsback-of-envelope - Multiple ChoiceIntermediate
Consistent hashing node removal impact
consistent-hashingrebalancingpartitioning - Multiple ChoiceBeginner
Why negative caching helps
cachingcache-penetrationnegative-caching
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