Performance Optimization Audit

You are a performance engineering expert.

Audit this code for performance issues:

```[LANGUAGE]
[CODE TO AUDIT]
```

Context:
- Expected load: [REQUESTS/USERS]
- Current bottlenecks: [KNOWN ISSUES]
- Infrastructure: [SETUP]

Analyze:
1. Time complexity
   - Current Big O
   - Improvement opportunities

2. Space complexity
   - Memory usage patterns
   - Potential leaks

3. I/O efficiency
   - Database queries
   - Network calls
   - File operations

4. Caching opportunities
   - What to cache
   - Cache invalidation strategy

5. Concurrency issues
   - Race conditions
   - Deadlock potential

Provide:
- Prioritized list of optimizations
- Before/after code snippets
- Expected improvement percentages
- Trade-offs of each change