Challenge Library
Preview challenges and watch demo simulations.
⏱
iOSSTOPWATCH
Difficulty★★☆☆☆
Levels7
Skills Tested
StatePersistenceConcurrencyRecovery
Estimated Time20–40 min
📝
WebTODO APP
Difficulty★★★☆☆
Levels7
Skills Tested
CRUDPersistenceOfflineConflict ResolutionMigrations
Estimated Time30–50 min
💬
WebCHAT APP
Difficulty★★★★☆
Levels7
Skills Tested
NetworkingReconnectionMessage OrderingOffline Queue
Estimated Time40–60 min
🛒
WebSHOPPING CART
Difficulty★★★☆☆
Levels6
Skills Tested
State ManagementPrice ChangesInventoryRace Conditions
Estimated Time25–45 min
📁
Distributed SystemsFILE SYNC ENGINE
Difficulty★★★★★
Levels7
Skills Tested
ConcurrencyConflictsCorrupted StateRetriesPartial Failures
Estimated Time50–80 min
🔐
SecurityAUTHENTICATION SYSTEM
Difficulty★★★★☆
Levels7
Skills Tested
SessionsExpirationAuthorizationToken HandlingSecurity
Estimated Time35–55 min
🔗
BackendURL SHORTENER
Difficulty★★★☆☆
Levels6
Skills Tested
API DesignPersistenceConcurrencyExpiration
Estimated Time25–40 min
⚡
AlgorithmsRATE LIMITER
Difficulty★★★★☆
Levels5
Skills Tested
ConcurrencyDistributed StateEdge CasesPerformance
Estimated Time30–50 min