Challenge Library
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.
Filter by type
Filter by difficulty
Popular topics
34 challenges matching your filters
Clear topic filter- Multiple ChoiceBeginner
Cache-aside vs write-through
system-designcaching - Multiple ChoiceBeginner
Write-back cache risk
system-designcaching - Multiple ChoiceBeginner
LRU vs LFU eviction
system-designcachingeviction - Multiple ChoiceHard
Cache stampede / thundering herd
system-designcachingstampede - Multiple ChoiceHard
Probabilistic early expiration
system-designcachingstampede - Multiple ChoiceBeginner
Negative caching
system-designcaching - Multiple ChoiceIntermediate
TTL jitter
system-designcaching - Multiple ChoiceBeginner
CDN purpose
system-designcachingcdn - Multiple ChoiceBeginner
Cache penetration
system-designcaching - 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 ChoiceIntermediate
Read-through cache
system-designcaching - Multiple ChoiceHard
Cache invalidation on write
system-designcachingcache-invalidation - Multiple ChoiceBeginner
Why negative caching helps
cachingcache-penetrationnegative-caching - Multiple ChoiceHard
URL Shortener Hot Key Mitigation
url-shortenerhot-keycaching - Multiple ChoiceIntermediate
Policy decision caching correctness
authorizationcachingpolicy-evaluation - Code AnalysisHard
Cache stampede on expiry
system-designcachingstampede - Code AnalysisBeginner
Cache key without entity version
system-designcachingcache-invalidation - Code AnalysisHard
Thundering herd with negative result
system-designcachingcache-penetration - Code AnalysisIntermediate
Cache eviction thrash
system-designcachingeviction - Code AnalysisIntermediate
Hot key in a cache cluster
system-designcachinghot-partition - Code AnalysisIntermediate
Read-through stampede on cold start
system-designcachingstampede - Code AnalysisIntermediate
Negative caching with wrong TTL
system-designcachingttl - Code AnalysisIntermediate
Double-write to cache and DB
system-designcachingcache-invalidation - Code AnalysisIntermediate
Thundering herd from synchronized cron
system-designcachingstampede - Code AnalysisIntermediate
Cache write without invalidation on update
system-designcachingcache-invalidation - Code AnalysisHard
Bloom filter with no eviction
system-designcachingbloom-filter - Code AnalysisBeginner
Cache aside stampede on hot key expiry
cachingstampedehot-key - Code AnalysisIntermediate
TTL jitter to prevent avalanche
cachingavalanchettl-jitter - Code AnalysisBeginner
Stale-while-revalidate cache bug
cachingswrcdn - Code AnalysisIntermediate
Cache key cardinality explosion
cachingcache-keyscardinality - Multiple ChoiceHard
Thundering herd on cache expiry
architectureresiliencecaching - Code AnalysisHard
Thundering herd on expiry
architectureresiliencecaching
Practice now, dominate the arena
Every challenge here is drawn from the live Code Royale pool. Review a question, then head to the arena to answer under pressure against a real opponent — 3-minute matches, Elo ranking, and badge tiers on the line.