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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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23 challenges matching your filters
Clear topic filter- Code AnalysisIntermediate
Self-deadlock from locking a non-recursive mutex twice
deadlockmutexconcurrency - Multiple ChoiceIntermediate
Why condition_variable wait needs a predicate loop
condition-variablespurious-wakeupconcurrency - Multiple ChoiceIntermediate
counting_semaphore acquire
semaphoreC++20concurrency - Multiple ChoiceBeginner
Counting Semaphore acquire/try_acquire
semaphoreconcurrencycpp20 - Multiple ChoiceHard
RCU Read-Side Guarantees
rcumemoryconcurrency - Multiple ChoiceIntermediate
Actor model: no shared mutable state
actor-modelconcurrency - Multiple ChoiceHard
Lost update race
system-designconcurrencyconsistency - Multiple ChoiceHard
Optimistic vs pessimistic locking
system-designconcurrencydatabases - Multiple ChoiceIntermediate
Preventing seat oversell
concurrencybookingoversell - Multiple ChoiceIntermediate
Oversell Prevention in Ticket Booking
bookinginventoryconcurrency - Multiple ChoiceBeginner
E-commerce oversell prevention approach
inventoryreservationconcurrency - Code AnalysisHard
Read-modify-write lost update
system-designconcurrencydatabases - Code AnalysisIntermediate
Full table lock from a long transaction
system-designdatabasesconcurrency - Code AnalysisHard
CAS retry livelock
system-designconcurrencydistributed-counter - Code AnalysisIntermediate
Deadlock from lock ordering
system-designdatabasesconcurrency - Code AnalysisHard
Idempotency key stored after the effect
system-designidempotencyconcurrency - Code AnalysisBeginner
Read-modify-write without atomicity
system-designconcurrencydistributed-counter - Code AnalysisHard
CAS without version on concurrent edit
system-designconcurrencydatabases - Code AnalysisIntermediate
Sync call in an async event loop
system-designscalabilityconcurrency - Code AnalysisHard
Lost update from read-modify-write
transactionslost-updateconcurrency - Code AnalysisIntermediate
Non-Atomic Balance Check SQL
sqlconcurrencytoctou - Code AnalysisHard
Idempotency: naive dedupe key
architectureidempotencyconcurrency - Code AnalysisHard
Aggregate Design for Concurrency
aggregatesconcurrencyddd
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