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
5,893 challenges total
- Multiple ChoiceHard
SSRF
backendhard - Multiple ChoiceIntermediate
Directory traversal
backendintermediate - Multiple ChoiceHard
Insecure deserialization
backendhard - Multiple ChoiceIntermediate
Credential stuffing
backendintermediate - Multiple ChoiceBeginner
Password complexity
backendbeginner - Multiple ChoiceIntermediate
Security headers
backendintermediate - Multiple ChoiceIntermediate
API key rotation
backendintermediate - Multiple ChoiceIntermediate
Zero-day vulnerability
backendintermediate - Multiple ChoiceIntermediate
Penetration testing
backendintermediate - Multiple ChoiceIntermediate
Bug bounty program
backendintermediate - Multiple ChoiceHard
Service mesh
backendhard - Multiple ChoiceHard
Sidecar pattern
backendhard - Multiple ChoiceIntermediate
Immutable deploys
backendintermediate - Multiple ChoiceHard
GitOps workflow
backendhard - Multiple ChoiceIntermediate
Progressive delivery
backendintermediate - Multiple ChoiceHard
Chaos engineering
backendhard - Multiple ChoiceIntermediate
Backup strategy (3-2-1)
backendintermediate - Multiple ChoiceIntermediate
IaC tools
backendintermediate - Multiple ChoiceIntermediate
Kubernetes namespaces
backendintermediate - Multiple ChoiceBeginner
Container registry
backendbeginner - Multiple ChoiceIntermediate
ConfigMap vs Secret
backendintermediate - Multiple ChoiceIntermediate
Health check types
backendintermediate - Multiple ChoiceHard
Log drivers
backendhard - Multiple ChoiceIntermediate
Build vs runtime stage
backendintermediate - Multiple ChoiceBeginner
Semantic versioning
backendbeginner - Multiple ChoiceIntermediate
Message serialization
backendintermediate - Multiple ChoiceHard
Event sourcing benefits
backendhard - Multiple ChoiceHard
Saga vs 2PC
backendhard - Multiple ChoiceHard
Data warehouse vs OLTP
backendhard - Multiple ChoiceIntermediate
Idempotency key pattern
backendintermediate - Multiple ChoiceIntermediate
Long polling
backendintermediate - Multiple ChoiceIntermediate
Graceful degradation
backendintermediate - Multiple ChoiceIntermediate
Failover strategy
backendintermediate - Multiple ChoiceHard
Concurrency control
backendhard - Multiple ChoiceIntermediate
Data sharding strategies
backendintermediate - Multiple ChoiceHard
Master election
backendhard - Multiple ChoiceHard
Quorum
backendhard - Multiple ChoiceHard
Backpressure strategies
backendhard - Multiple ChoiceHard
Circuit Breaker — Half-Open State
backendhard - Multiple ChoiceHard
Bulkhead pattern
backendhard - Multiple ChoiceBeginner
HTTP Methods
backendbeginner - Multiple ChoiceIntermediate
Idempotent Methods
backendintermediate - Multiple ChoiceBeginner
Status 200
backendbeginner - Multiple ChoiceBeginner
Status 201
backendbeginner - Multiple ChoiceIntermediate
Status 301 vs 302
backendintermediate - Multiple ChoiceBeginner
Status 400
backendbeginner - Multiple ChoiceIntermediate
Status 401 vs 403
backendintermediate - Multiple ChoiceBeginner
Status 404
backendbeginner - Multiple ChoiceBeginner
Status 500
backendbeginner - Multiple ChoiceIntermediate
Status 502/503
backendintermediate - Multiple ChoiceIntermediate
REST Constraints
backendintermediate - Multiple ChoiceIntermediate
REST Resources
backendintermediate - Multiple ChoiceBeginner
HTTP Headers
backendbeginner - Multiple ChoiceBeginner
Content-Type Header
backendbeginner - Multiple ChoiceIntermediate
Accept Header
backendintermediate - Multiple ChoiceIntermediate
CORS Headers
backendintermediate - Multiple ChoiceIntermediate
Cache-Control
backendintermediate - Multiple ChoiceIntermediate
ETag Header
backendintermediate - Multiple ChoiceIntermediate
Query vs Path Params
backendintermediate - Multiple ChoiceBeginner
Request Body
backendbeginner
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.