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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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1,344 challenges matching your filters
- Multiple ChoiceHard
Architecture quantum and independent deployability
architecture-quantumevolutionary-architecture - Multiple ChoiceHard
Expand-contract: safe schema evolution
expand-contractschema-evolutionzero-downtime - Multiple ChoiceHard
Specification pattern reuse
specificationdomain-model - Multiple ChoiceHard
Service Mesh mTLS
mtlsservice-meshsecurity - Multiple ChoiceHard
CRDT vs OT for collaborative editing
crdtcollaborative-editingot - Multiple ChoiceHard
Local-first software trade-offs
local-firsttrade-offsconsistency - Multiple ChoiceHard
Duplication vs wrong abstraction
duplicationdryrule-of-three - Multiple ChoiceHard
Deep inheritance hierarchies
inheritancecompositionrefactoring - Multiple ChoiceHard
LSP violations in practice
lspsolidcollections - Multiple ChoiceHard
DIP at boundaries
diphexagonalports - Multiple ChoiceHard
Cell-Based Architecture Rationale
cell-basedblast-radiusresilience - Multiple ChoiceHard
Avoiding Dual-Write Problems
dual-writeconsistencyanti-pattern - Multiple ChoiceHard
Saga Compensation Correctness
sagacompensationidempotency - Multiple ChoiceHard
Retry Budgets and Amplification
retry-budgetamplificationresilience - Multiple ChoiceHard
Load Shedding vs Queueing
load-sheddingoverloadbackpressure - Multiple ChoiceHard
[System Design] Cache-aside Reduce latency
qasys-designsys-designqa - Multiple ChoiceHard
[System Design] Write-through Reduce latency
qasys-designsys-designqa - Multiple ChoiceHard
[System Design] Write-behind Reduce latency
qasys-designsys-designqa - Multiple ChoiceHard
[System Design] TTL and invalidation Reduce latency
qasys-designsys-designqa - Multiple ChoiceHard
[System Design] Cache stampede Reduce latency
qasys-designsys-designqa - Multiple ChoiceHard
[System Design] States Fail fast for failing services
qasys-designsys-designqa - Multiple ChoiceHard
[System Design] Threshold Fail fast for failing services
qasys-designsys-designqa - Multiple ChoiceHard
[System Design] Fallback Fail fast for failing services
qasys-designsys-designqa - Multiple ChoiceHard
[System Design] Half-open test Fail fast for failing services
qasys-designsys-designqa - Multiple ChoiceHard
[System Design] Benefits Fail fast for failing services
qasys-designsys-designqa - Multiple ChoiceHard
[System Design] Command Separate read and write models
qasys-designsys-designqa - Multiple ChoiceHard
[System Design] Query Separate read and write models
qasys-designsys-designqa - Multiple ChoiceHard
[System Design] CQRS Separate read and write models
qasys-designsys-designqa - Multiple ChoiceHard
[System Design] Materialized view Separate read and write models
qasys-designsys-designqa - Multiple ChoiceHard
[System Design] Eventual consistency Separate read and write models
qasys-designsys-designqa - Multiple ChoiceHard
[System Design] Key pattern Safe retries
qasys-designsys-designqa - Multiple ChoiceHard
[System Design] Stripe pattern Safe retries
qasys-designsys-designqa - Multiple ChoiceHard
[System Design] Idempotent HTTP Safe retries
qasys-designsys-designqa - Multiple ChoiceHard
[System Design] Duplicate detection Safe retries
qasys-designsys-designqa - Multiple ChoiceHard
[System Design] TTL on keys Safe retries
qasys-designsys-designqa - Multiple ChoiceHard
[System Design] Producer/consumer Async decoupling
qasys-designsys-designqa - Multiple ChoiceHard
[System Design] At-least-once Async decoupling
qasys-designsys-designqa - Multiple ChoiceHard
[System Design] DLQ Async decoupling
qasys-designsys-designqa - Multiple ChoiceHard
[System Design] Kafka vs RabbitMQ Async decoupling
qasys-designsys-designqa - Multiple ChoiceHard
[System Design] Backpressure Async decoupling
qasys-designsys-designqa - Multiple ChoiceHard
[System Design] Three pillars Monitor system health
qasys-designsys-designqa - Multiple ChoiceHard
[System Design] Prometheus Monitor system health
qasys-designsys-designqa - Multiple ChoiceHard
[System Design] Grafana Monitor system health
qasys-designsys-designqa - Multiple ChoiceHard
[System Design] Distributed tracing Monitor system health
qasys-designsys-designqa - Multiple ChoiceHard
[System Design] SLI/SLO/SLA Monitor system health
qasys-designsys-designqa - Multiple ChoiceHard
[System Design] Shard key Horizontal partition
qasys-designsys-designqa - Multiple ChoiceHard
[System Design] Range vs hash Horizontal partition
qasys-designsys-designqa - Multiple ChoiceHard
[System Design] Rebalance Horizontal partition
qasys-designsys-designqa - Multiple ChoiceHard
[System Design] Cross-shard joins Horizontal partition
qasys-designsys-designqa - Multiple ChoiceHard
[System Design] Consistent hashing Horizontal partition
qasys-designsys-designqa - 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
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