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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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18 challenges matching your filters
Clear topic filter- Multiple ChoiceBeginner
Read replica lag
system-designdatabasesreplication - Multiple ChoiceBeginner
SQL vs NoSQL access pattern
system-designdatabasesnosql - Multiple ChoiceBeginner
Index write amplification
system-designdatabasesindexes - Multiple ChoiceHard
Sharding key choice
system-designdatabasessharding - Multiple ChoiceIntermediate
Read-heavy vs write-heavy design
system-designcapacity-estimationdatabases - Multiple ChoiceHard
Optimistic vs pessimistic locking
system-designconcurrencydatabases - Code AnalysisHard
N+1 query in an ORM loop
system-designdatabasesn-plus-one - Code AnalysisHard
Read-modify-write lost update
system-designconcurrencydatabases - Code AnalysisBeginner
NULL comparison bug
system-designdatabasessql - Code AnalysisIntermediate
Implicit type cast kills index
system-designdatabasesindexes - Code AnalysisBeginner
Unbounded SELECT without index
system-designdatabasesindexesreplication - Code AnalysisBeginner
Missing index on a foreign-key join
system-designdatabasesindexes - Code AnalysisIntermediate
Full table lock from a long transaction
system-designdatabasesconcurrency - Code AnalysisBeginner
Thundering herd on connection pool resize
system-designdatabasesconnection-pool - Code AnalysisIntermediate
Deadlock from lock ordering
system-designdatabasesconcurrency - Code AnalysisIntermediate
Selective column over-fetch
system-designdatabasesperformance - Code AnalysisBeginner
Writing to a replica
system-designdatabasesreplication - Code AnalysisHard
CAS without version on concurrent edit
system-designconcurrencydatabases
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