Challenges

Master AI-assisted coding through hands-on practice

33 challenges

6 categories

All Easy Medium Hard|Backend Frontend Incident Resolution DevOps Database AI Skills

Fix the Broken Layout

A flexbox layout is not behaving as expected. The sidebar should stay fixed while content scrolls.

Fix the Null Reference Bug

A REST API endpoint is crashing with a null reference error. Find and fix the bug that occurs when optional user data is missing.

Build a Todo API

Create a simple REST API for managing todos. Implement CRUD operations with the provided Express app skeleton.

Build a Rate Limiter

Implement a rate limiting middleware that limits requests per IP address. Start with the provided skeleton and complete the implementation.

Fix the Middleware Order

Authentication middleware is not protecting routes correctly. The order of middleware matters!

Fix the Async/Await Bug

An async function is not waiting for data to load before processing. Fix the promise handling issue.

The Event Emitter Memory Mystery

This Node.js application has a subtle memory behavior. Analyze the code and predict what will happen when processData is called 1000 times. Explain the memory implications.

Explain: Event Loop Behavior

Analyze this code and predict the output order. Explain why the output appears in that order.

Fix the Stale Closure

A counter component shows incorrect values due to a stale closure in the event handler. Fix the state management issue.

Fix the Infinite Re-render

A React component is causing an infinite re-render loop. Find and fix the useEffect dependency issue.

SEV1: Payment Service Outage

Critical incident: The payment service is down in production. Users cannot complete purchases. You are the on-call engineer - investigate the dashboards, logs, and traces to identify the root cause and determine the remediation steps.

The Cache Stampede Crisis

IncidentHardPremium

After a cache server restart, the database is being overwhelmed with requests. Diagnose the cache stampede and propose solutions.

Debug API Gateway Timeouts

Users are experiencing intermittent 504 timeout errors. Investigate the system to find the root cause and propose fixes.

Fix Connection Pool Exhaustion

DebugHardPremium

API requests are timing out. The database connection pool is being exhausted due to leaked connections.

Diagnose the Memory Leak

DebugHardPremium

Production servers are running out of memory. Analyze the code and logs to find the memory leak.

Fix Terraform State Issues

RefactorHardPremium

A Terraform configuration has state management problems causing conflicts in team environments. Fix the backend configuration.

Fix Docker Compose Networking

Services in a Docker Compose stack cannot communicate with each other. Debug and fix the networking configuration.

Fix the Kubernetes Deployment

A Kubernetes deployment is failing to start. Debug the manifest and fix the configuration issues preventing pods from running.

Fix the CI Pipeline

The GitHub Actions workflow is failing. Debug and fix the configuration issues.

Optimize the Dockerfile

A Docker build is taking too long and creating huge images. Optimize the Dockerfile for faster builds and smaller images.

E-commerce Checkout Security Review

Code ReviewHardPremium

Review this checkout system code for security vulnerabilities, data validation issues, and potential exploits. Document all issues you find.

Code Review: Security Audit

Code ReviewHard

Review this authentication code and identify all security vulnerabilities. Document your findings in the review.md file.

Analyze the Database Deadlock

Production transactions are failing with deadlock errors. Analyze the code to identify the deadlock pattern and propose a fix.

Fix the N+1 Query Problem

RefactorHardPremium

An API endpoint is making hundreds of database queries when it should only make one. Optimize the data fetching.

Fix SQL Injection Vulnerability

A database query is vulnerable to SQL injection attacks. Fix the security issue using parameterized queries.

Analyze Payment Retry Logic

Analyze a complex requirement for payment retry functionality. Consider failure scenarios, security implications, and user experience.

Analyze User Notification System

Analyze a requirement for a user notification system. Identify edge cases, write user stories, and ask clarifying questions.

Document the Event System

Create comprehensive documentation for a TypeScript event emitter system. Focus on type safety and usage patterns.

Document the Cache Module

Write AI-consumable documentation for a caching utility module. Include setup, usage examples, and API reference.

Verify the API Documentation

An AI generated API documentation. Spot the inaccuracies, made-up endpoints, and incorrect information before publishing.

The Shopping Cart Mystery

Customers are complaining about wrong totals in their shopping carts! Some orders show $NaN, others have incorrect amounts. Can you find the bugs before Black Friday?

Review the Authentication PR

An AI generated a PR for JWT token refresh functionality. Find the hallucinations, logic errors, and security issues before it gets merged.

The Mysterious Login Failures

DebugHardPremium

Users report intermittent login failures. The auth service works fine in development but fails randomly in production under load. Find and fix the race condition.