Async/Await Patterns

Refactor and optimize the asynchronous programming in the following [PROGRAMMING LANGUAGE] code:

**Current Code:**
```[PROGRAMMING LANGUAGE]
[INSERT CODE HERE]
```

**Please analyze and improve:**
1. **Parallelization:** Identify independent async operations and run them in parallel (Promise.all, asyncio.gather, etc.)
2. **Error Handling:** Implement correct error handling for all async paths
3. **Race Conditions:** Identify and fix potential race conditions
4. **Cancellation:** Implement cancellation capabilities (AbortController, CancellationToken)
5. **Throttling/Debouncing:** Limit parallel requests where needed
6. **Memory Leaks:** Check for unhandled promises and missing cleanup logic
7. **Timeout Handling:** Add timeouts for external calls

**Patterns to check:**
- Sequential vs. parallel execution
- Promise.allSettled for fault-tolerant parallelism
- Async iterators for streaming
- Semaphore pattern for limited concurrency

Show the optimized code with explanations.

Replace placeholders in [square brackets]: [PROGRAMMING LANGUAGE][INSERT CODE HERE]