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
350 challenges matching your filters
Clear topic filter- Multiple ChoiceHard
[Git] Regression Binary search to find bug-introducing commit
qagitgitqa - Multiple ChoiceHard
[Git] Mark bad Binary search to find bug-introducing commit
qagitgitqa - Multiple ChoiceHard
[Git] Automated Binary search to find bug-introducing commit
qagitgitqa - Multiple ChoiceHard
[Git] Reset Binary search to find bug-introducing commit
qagitgitqa - Multiple ChoiceHard
[Git] Skip Binary search to find bug-introducing commit
qagitgitqa - Multiple ChoiceHard
[Git] Lost commits Local history of HEAD movements
qagitgitqa - Multiple ChoiceHard
[Git] Show all Local history of HEAD movements
qagitgitqa - Multiple ChoiceHard
[Git] Branch recovery Local history of HEAD movements
qagitgitqa - Multiple ChoiceHard
[Git] Timestamps Local history of HEAD movements
qagitgitqa - Multiple ChoiceHard
[Git] Restore Local history of HEAD movements
qagitgitqa - Multiple ChoiceHard
[Git] Add Embed external repositories within a repo
qagitgitqa - Multiple ChoiceHard
[Git] After clone Embed external repositories within a repo
qagitgitqa - Multiple ChoiceHard
[Git] Remove Embed external repositories within a repo
qagitgitqa - Multiple ChoiceHard
[Git] Foreach Embed external repositories within a repo
qagitgitqa - Multiple ChoiceHard
[Git] Sync Embed external repositories within a repo
qagitgitqa - Multiple ChoiceHard
[Go] Syntax Type parameters for reusable code
qagogoqa - Multiple ChoiceHard
[Go] Constraint Type parameters for reusable code
qagogoqa - Multiple ChoiceHard
[Go] Comparable Type parameters for reusable code
qagogoqa - Multiple ChoiceHard
[Go] Type sets Type parameters for reusable code
qagogoqa - Multiple ChoiceHard
[Go] Generic types Type parameters for reusable code
qagogoqa - Multiple ChoiceHard
[Go] First ready Multi-channel operation
qagogoqa - Multiple ChoiceHard
[Go] Default Multi-channel operation
qagogoqa - Multiple ChoiceHard
[Go] Timeout Multi-channel operation
qagogoqa - Multiple ChoiceHard
[Go] Nil channel Multi-channel operation
qagogoqa - Multiple ChoiceHard
[Go] Fair Multi-channel operation
qagogoqa - Multiple ChoiceHard
[Go] Mutex Concurrency primitives
qagogoqa - Multiple ChoiceHard
[Go] WaitGroup Concurrency primitives
qagogoqa - Multiple ChoiceHard
[Go] sync.Once Concurrency primitives
qagogoqa - Multiple ChoiceHard
[Go] Cond Concurrency primitives
qagogoqa - Multiple ChoiceHard
[Go] Pool Concurrency primitives
qagogoqa - Multiple ChoiceHard
[GraphQL] Default Field resolution functions
qagraphqlgraphqlqa - Multiple ChoiceHard
[GraphQL] Arguments Field resolution functions
qagraphqlgraphqlqa - Multiple ChoiceHard
[GraphQL] N+1 problem Field resolution functions
qagraphqlgraphqlqa - Multiple ChoiceHard
[GraphQL] DataLoader Field resolution functions
qagraphqlgraphqlqa - Multiple ChoiceHard
[GraphQL] Async Field resolution functions
qagraphqlgraphqlqa - Multiple ChoiceHard
[GraphQL] SDL Type system definition
qagraphqlgraphqlqa - Multiple ChoiceHard
[GraphQL] Object types Type system definition
qagraphqlgraphqlqa - Multiple ChoiceHard
[GraphQL] Scalars Type system definition
qagraphqlgraphqlqa - Multiple ChoiceHard
[GraphQL] Enums Type system definition
qagraphqlgraphqlqa - Multiple ChoiceHard
[GraphQL] Unions/Interfaces Type system definition
qagraphqlgraphqlqa - Multiple ChoiceHard
[GraphQL] WebSocket Real-time events
qagraphqlgraphqlqa - Multiple ChoiceHard
[GraphQL] Subscribe Real-time events
qagraphqlgraphqlqa - Multiple ChoiceHard
[GraphQL] PubSub engine Real-time events
qagraphqlgraphqlqa - Multiple ChoiceHard
[GraphQL] Filter Real-time events
qagraphqlgraphqlqa - Multiple ChoiceHard
[GraphQL] Auth Real-time events
qagraphqlgraphqlqa - Multiple ChoiceHard
[HTTP API] ETag Reduce server load and latency
qahttphttpqa - Multiple ChoiceHard
[HTTP API] Last-Modified Reduce server load and latency
qahttphttpqa - Multiple ChoiceHard
[HTTP API] no-store Reduce server load and latency
qahttphttpqa - Multiple ChoiceHard
[HTTP API] Max-age Reduce server load and latency
qahttphttpqa - Multiple ChoiceHard
[HTTP API] Vary Reduce server load and latency
qahttphttpqa - Multiple ChoiceHard
[HTTP API] Protobuf RPC framework using Protocol Buffers
qahttphttpqa - Multiple ChoiceHard
[HTTP API] Stream types RPC framework using Protocol Buffers
qahttphttpqa - Multiple ChoiceHard
[HTTP API] HTTP/2 RPC framework using Protocol Buffers
qahttphttpqa - Multiple ChoiceHard
[HTTP API] Service def RPC framework using Protocol Buffers
qahttphttpqa - Multiple ChoiceHard
[HTTP API] Deadlines RPC framework using Protocol Buffers
qahttphttpqa - Multiple ChoiceHard
[HTTP API] Stateless Architectural constraints for APIs
qahttphttpqa - Multiple ChoiceHard
[HTTP API] Resource URLs Architectural constraints for APIs
qahttphttpqa - Multiple ChoiceHard
[HTTP API] HATEOAS Architectural constraints for APIs
qahttphttpqa - Multiple ChoiceHard
[HTTP API] Uniform interface Architectural constraints for APIs
qahttphttpqa - Multiple ChoiceHard
[HTTP API] Content negotiation Architectural constraints for APIs
qahttphttpqa
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.