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.

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All types Multiple Choice Code Analysis Code

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350 challenges matching your filters

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Multiple ChoiceHard
[System Design] Key pattern Safe retries
qasys-designsys-designqa
Multiple ChoiceHard
[System Design] Stripe pattern Safe retries
qasys-designsys-designqa
Multiple ChoiceHard
[System Design] Idempotent HTTP Safe retries
qasys-designsys-designqa
Multiple ChoiceHard
[System Design] Duplicate detection Safe retries
qasys-designsys-designqa
Multiple ChoiceHard
[System Design] TTL on keys Safe retries
qasys-designsys-designqa
Multiple ChoiceHard
[System Design] Producer/consumer Async decoupling
qasys-designsys-designqa
Multiple ChoiceHard
[System Design] At-least-once Async decoupling
qasys-designsys-designqa
Multiple ChoiceHard
[System Design] DLQ Async decoupling
qasys-designsys-designqa
Multiple ChoiceHard
[System Design] Kafka vs RabbitMQ Async decoupling
qasys-designsys-designqa
Multiple ChoiceHard
[System Design] Backpressure Async decoupling
qasys-designsys-designqa
Multiple ChoiceHard
[System Design] Three pillars Monitor system health
qasys-designsys-designqa
Multiple ChoiceHard
[System Design] Prometheus Monitor system health
qasys-designsys-designqa
Multiple ChoiceHard
[System Design] Grafana Monitor system health
qasys-designsys-designqa
Multiple ChoiceHard
[System Design] Distributed tracing Monitor system health
qasys-designsys-designqa
Multiple ChoiceHard
[System Design] SLI/SLO/SLA Monitor system health
qasys-designsys-designqa
Multiple ChoiceHard
[System Design] Shard key Horizontal partition
qasys-designsys-designqa
Multiple ChoiceHard
[System Design] Range vs hash Horizontal partition
qasys-designsys-designqa
Multiple ChoiceHard
[System Design] Rebalance Horizontal partition
qasys-designsys-designqa
Multiple ChoiceHard
[System Design] Cross-shard joins Horizontal partition
qasys-designsys-designqa
Multiple ChoiceHard
[System Design] Consistent hashing Horizontal partition
qasys-designsys-designqa
Multiple ChoiceHard
[Testing] Playwright Test full user flows
qatestingtestingqa
Multiple ChoiceHard
[Testing] Page Object Model Test full user flows
qatestingtestingqa
Multiple ChoiceHard
[Testing] Visual testing Test full user flows
qatestingtestingqa
Multiple ChoiceHard
[Testing] Flaky tests Test full user flows
qatestingtestingqa
Multiple ChoiceHard
[Testing] CI integration Test full user flows
qatestingtestingqa
Multiple ChoiceHard
[TypeScript] ReturnType Extract types in conditionals
qatypescripttypescriptqa
Multiple ChoiceHard
[TypeScript] Promise unwrap Extract types in conditionals
qatypescripttypescriptqa
Multiple ChoiceHard
[TypeScript] Array element Extract types in conditionals
qatypescripttypescriptqa
Multiple ChoiceHard
[TypeScript] Function param Extract types in conditionals
qatypescripttypescriptqa
Multiple ChoiceHard
[TypeScript] Co-variance Extract types in conditionals
qatypescripttypescriptqa
Multiple ChoiceHard
[TypeScript] typeof Refine union types
qatypescripttypescriptqa
Multiple ChoiceHard
[TypeScript] instanceof Refine union types
qatypescripttypescriptqa
Multiple ChoiceHard
[TypeScript] in Refine union types
qatypescripttypescriptqa
Multiple ChoiceHard
[TypeScript] is predicate Refine union types
qatypescripttypescriptqa
Multiple ChoiceHard
[TypeScript] asserts Refine union types
qatypescripttypescriptqa
Multiple ChoiceHard
[TypeScript] Partial<T> Built-in type transforms
qatypescripttypescriptqa
Multiple ChoiceHard
[TypeScript] Required<T> Built-in type transforms
qatypescripttypescriptqa
Multiple ChoiceHard
[TypeScript] Pick<T,K> Built-in type transforms
qatypescripttypescriptqa
Multiple ChoiceHard
[TypeScript] Omit<T,K> Built-in type transforms
qatypescripttypescriptqa
Multiple ChoiceHard
[TypeScript] Record<K,V> Built-in type transforms
qatypescripttypescriptqa
Multiple ChoiceHard
[Webpack] Dynamic import Lazy load parts of app
qawebpackwebpackqa
Multiple ChoiceHard
[Webpack] SplitChunks Lazy load parts of app
qawebpackwebpackqa
Multiple ChoiceHard
[Webpack] Vendor bundle Lazy load parts of app
qawebpackwebpackqa
Multiple ChoiceHard
[Webpack] Prefetch Lazy load parts of app
qawebpackwebpackqa
Multiple ChoiceHard
[Webpack] Lazy routes Lazy load parts of app
qawebpackwebpackqa
Multiple ChoiceHard
[Webpack] ESM required Remove unused exports
qawebpackwebpackqa
Multiple ChoiceHard
[Webpack] Side effects flag Remove unused exports
qawebpackwebpackqa
Multiple ChoiceHard
[Webpack] Production mode Remove unused exports
qawebpackwebpackqa
Multiple ChoiceHard
[Webpack] CommonJS Remove unused exports
qawebpackwebpackqa
Multiple ChoiceHard
[Webpack] Lodash Remove unused exports
qawebpackwebpackqa

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.

Coding Challenges

[System Design] Key pattern Safe retries

[System Design] Stripe pattern Safe retries

[System Design] Idempotent HTTP Safe retries

[System Design] Duplicate detection Safe retries

[System Design] TTL on keys Safe retries

[System Design] Producer/consumer Async decoupling

[System Design] At-least-once Async decoupling

[System Design] DLQ Async decoupling

[System Design] Kafka vs RabbitMQ Async decoupling

[System Design] Backpressure Async decoupling

[System Design] Three pillars Monitor system health

[System Design] Prometheus Monitor system health

[System Design] Grafana Monitor system health

[System Design] Distributed tracing Monitor system health

[System Design] SLI/SLO/SLA Monitor system health

[System Design] Shard key Horizontal partition

[System Design] Range vs hash Horizontal partition

[System Design] Rebalance Horizontal partition

[System Design] Cross-shard joins Horizontal partition

[System Design] Consistent hashing Horizontal partition

[Testing] Playwright Test full user flows

[Testing] Page Object Model Test full user flows

[Testing] Visual testing Test full user flows

[Testing] Flaky tests Test full user flows

[Testing] CI integration Test full user flows

[TypeScript] ReturnType Extract types in conditionals

[TypeScript] Promise unwrap Extract types in conditionals

[TypeScript] Array element Extract types in conditionals

[TypeScript] Function param Extract types in conditionals

[TypeScript] Co-variance Extract types in conditionals

[TypeScript] typeof Refine union types

[TypeScript] instanceof Refine union types

[TypeScript] in Refine union types

[TypeScript] is predicate Refine union types

[TypeScript] asserts Refine union types

[TypeScript] Partial<T> Built-in type transforms

[TypeScript] Required<T> Built-in type transforms

[TypeScript] Pick<T,K> Built-in type transforms

[TypeScript] Omit<T,K> Built-in type transforms

[TypeScript] Record<K,V> Built-in type transforms

[Webpack] Dynamic import Lazy load parts of app

[Webpack] SplitChunks Lazy load parts of app

[Webpack] Vendor bundle Lazy load parts of app

[Webpack] Prefetch Lazy load parts of app

[Webpack] Lazy routes Lazy load parts of app

[Webpack] ESM required Remove unused exports

[Webpack] Side effects flag Remove unused exports

[Webpack] Production mode Remove unused exports

[Webpack] CommonJS Remove unused exports

[Webpack] Lodash Remove unused exports

Practice now, dominate the arena