Software Engineering

You are a senior API architect. Design a RESTful API for:

Project: [DESCRIBE YOUR APPLICATION]
Core entities: [LIST MAIN DATA OBJECTS]
Key operations: [LIST WHAT USERS NEED TO DO]

Provide:
1. Endpoint structure (URL patterns)
2. HTTP methods for each endpoint
3. Request/response schemas (JSON)
4. Authentication approach
5. Error handling patterns
6. Pagination strategy

You are a senior software engineer conducting a code review. Analyze the following code for:

1. Bugs & Logic Errors: Identify any potential bugs or logical issues
2. Performance: Suggest optimizations for better performance
3. Security: Flag any security vulnerabilities
4. Best Practices: Recommend improvements based on industry best practices
5. Readability: Suggest ways to improve code clarity

Be specific with line numbers and provide concrete suggestions with code examples.

Code to review:
[PASTE CODE HERE]

You are an expert debugger. Help solve this issue.

Error/Problem: [DESCRIBE THE ERROR]
Code: [PASTE RELEVANT CODE]
Expected behavior: [WHAT SHOULD HAPPEN]
Actual behavior: [WHAT IS HAPPENING]

Please:
1. Identify the root cause
2. Explain why this is happening
3. Provide a fix with code
4. Suggest how to prevent this in the future

I need to refactor this legacy code. Please analyze it and suggest improvements:

```
[PASTE CODE HERE]
```

**Context:**
- Language/Framework: [specify]
- This code does: [brief description]
- Pain points: [what's wrong with it]

Provide:
1. Code smell identification
2. Step-by-step refactoring plan (small, safe changes)
3. Refactored code with explanations
4. Tests I should add before/after
5. Potential risks of the refactoring

Prioritize maintainability and readability over cleverness.

I'm preparing for a system design interview. Help me design a system for:

**System:** [e.g., URL shortener, Twitter feed, Uber]
**Scale:** [expected users/requests]
**Constraints:** [any specific requirements]

Walk me through:
1. Requirements clarification (functional & non-functional)
2. Back-of-envelope capacity estimation
3. High-level design with diagram description
4. Data model and database choices
5. API design
6. Detailed component design
7. Scaling strategies and bottlenecks
8. Trade-offs discussion

Ask clarifying questions first, then proceed step by step.

Write production-ready code for the following requirement:

**Task:** [describe what the code should do]
**Language:** [programming language]
**Context:** [where this will run, any constraints]

The code must include:
- Proper error handling with meaningful messages
- Input validation
- Logging at appropriate levels
- Type hints/annotations
- Comprehensive docstrings/comments
- Unit tests
- Edge case handling

Follow [language] best practices and style guides. Explain any design decisions.