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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2,019 challenges matching your filters
- 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 - Multiple ChoiceIntermediate
Consistent hashing node removal impact
consistent-hashingrebalancingpartitioning - Multiple ChoiceIntermediate
Quorum read-write overlap formula
quorumreplicationconsistency - Multiple ChoiceIntermediate
Exactly-once via idempotent producer
kafkaexactly-oncetransactions - Multiple ChoiceIntermediate
GraphQL resolver N+1
graphqln+1batching - Multiple ChoiceIntermediate
Error budget burn policy
sloerror-budgetreliability - Multiple ChoiceIntermediate
Tail sampling versus head sampling
tracingtail-samplingobservability - Multiple ChoiceIntermediate
Data residency constraint enforcement
gdprdata-residencycompliance - Multiple ChoiceIntermediate
Size-tiered vs leveled compaction
lsmcompactionwrite-amplification - Multiple ChoiceIntermediate
B+tree vs LSM read/write trade-off
btreelsmtrade-offs - Multiple ChoiceIntermediate
Connection pool sizing math
connection-poolsizingcapacity - Multiple ChoiceIntermediate
Preventing seat oversell
concurrencybookingoversell - Multiple ChoiceIntermediate
Saga Choreography vs Orchestration Tradeoff
sagaorchestrationchoreography - Multiple ChoiceIntermediate
Fan-Out on Write vs Read
news-feedfan-outcelebrity - Multiple ChoiceIntermediate
Stable Cursor Pagination
paginationfeedcursor - Multiple ChoiceIntermediate
Per-Conversation Ordering in Chat
chatorderingreceipts - Multiple ChoiceIntermediate
Oversell Prevention in Ticket Booking
bookinginventoryconcurrency - Multiple ChoiceIntermediate
Geohash vs S2 for Radius Search
proximitys2geohash - Multiple ChoiceIntermediate
Consistent Rollout via Hashing
feature-flagsrollouthashing - Multiple ChoiceIntermediate
Config Service Watch for Updates
configwatchpush - Multiple ChoiceIntermediate
API Gateway Circuit Breaking
api-gatewaycircuit-breakerresilience - Multiple ChoiceIntermediate
Multi-region failover RTO vs RPO
multi-regionfailoverrto-rpo - Multiple ChoiceIntermediate
ETL vs ELT for schema drift
data-pipelineeltschema-drift - Multiple ChoiceIntermediate
Distributed tracing tail sampling rationale
tracingsamplingobservability - Multiple ChoiceIntermediate
Refresh token rotation security
oauth2refresh-tokenrotationsecurity - Multiple ChoiceIntermediate
Policy decision caching correctness
authorizationcachingpolicy-evaluation - Multiple ChoiceIntermediate
[Testing] Line Code execution measurement
qatestingtestingqa - Multiple ChoiceIntermediate
[Testing] Branch Code execution measurement
qatestingtestingqa - Multiple ChoiceIntermediate
[Testing] Mutation Code execution measurement
qatestingtestingqa - Multiple ChoiceIntermediate
[Testing] 80% myth Code execution measurement
qatestingtestingqa - Multiple ChoiceIntermediate
[Testing] Threshold CI Code execution measurement
qatestingtestingqa - Multiple ChoiceIntermediate
[Testing] Test database Test cross-component interaction
qatestingtestingqa - Multiple ChoiceIntermediate
[Testing] Testcontainers Test cross-component interaction
qatestingtestingqa - Multiple ChoiceIntermediate
[Testing] Contract testing Test cross-component interaction
qatestingtestingqa - Multiple ChoiceIntermediate
[Testing] Seed data Test cross-component interaction
qatestingtestingqa - Multiple ChoiceIntermediate
[Testing] Teardown Test cross-component interaction
qatestingtestingqa - Multiple ChoiceIntermediate
[Testing] Function mock Simulate dependencies
qatestingtestingqa - Multiple ChoiceIntermediate
[Testing] Module mock Simulate dependencies
qatestingtestingqa - Multiple ChoiceIntermediate
[Testing] Spy Simulate dependencies
qatestingtestingqa - Multiple ChoiceIntermediate
[Testing] Partial mock Simulate dependencies
qatestingtestingqa - Multiple ChoiceIntermediate
[Testing] Reset Simulate dependencies
qatestingtestingqa - Multiple ChoiceIntermediate
[Testing] Jest Compare against stored output
qatestingtestingqa - Multiple ChoiceIntermediate
[Testing] Update flow Compare against stored output
qatestingtestingqa - Multiple ChoiceIntermediate
[Testing] Version control Compare against stored output
qatestingtestingqa - Multiple ChoiceIntermediate
[Testing] Regression Compare against stored output
qatestingtestingqa - Multiple ChoiceIntermediate
[Testing] Inline Compare against stored output
qatestingtestingqa - Multiple ChoiceIntermediate
[Testing] Red Red-Green-Refactor
qatestingtestingqa - Multiple ChoiceIntermediate
[Testing] Green Red-Green-Refactor
qatestingtestingqa
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