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Millennium Management·Software Engineer·Technical Phone Screen·Intermediate

Intermediate
Jun 2026

Summary

Did a technical screen for a software engineer role at Millennium Management centered entirely on async Python debugging. One question, pretty deep, and I left feeling like I'd half-explained my way through it.

Questions Asked (1)

Q1

You're given a Python pseudocode snippet that sequentially calls HTTP APIs and processes the returned data, but the main program doesn't print the expected result. How do you diagnose the root cause and fix it, given it likely involves improper async handling?

API & IntegrationsRoot Cause AnalysisTechnical Trade-offs
Author's notes

The core issue was that someone had kicked off coroutines without awaiting them, so the print statement ran before anything actually resolved.

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AI HintsAI Generated

Suggested Approach

Start by explaining how you would reproduce the issue and inspect the code for missing await/async keywords or unawaited coroutines. Then walk through a systematic debugging process: check for silent exceptions, verify event loop usage, and ensure proper synchronization. Finally, propose a fix and discuss how to prevent similar issues.

Pro tip: Mention that unawaited coroutines often produce a RuntimeWarning that can be caught by enabling warnings or using asyncio debug mode. This shows you know how to surface silent failures quickly.

1. Reproduce and Observe

Run the code and capture any warnings or errors. Check if the program exits prematurely or hangs, and note what is printed versus expected.

2. Inspect Async Usage

Look for missing 'await' keywords, functions defined as async but called without await, or blocking calls inside async functions. Verify that all coroutines are properly scheduled.

3. Check Event Loop and Concurrency

Ensure the event loop is running and that tasks are awaited or gathered. Look for improper use of asyncio.run, loop.run_until_complete, or mixing sync/async code.

4. Isolate and Test

Add logging or breakpoints to trace execution flow. Test individual API calls and async functions in isolation to pinpoint where the chain breaks.

5. Fix and Validate

Apply the fix (e.g., add await, use asyncio.gather, refactor to async). Re-run and verify output. Consider adding tests or linting to catch similar issues.

Key Points to Mention

  • Unawaited coroutines and RuntimeWarning
  • Proper use of asyncio.run, asyncio.gather, and await
  • Blocking calls in async code (e.g., requests vs aiohttp)
  • Event loop management and task scheduling
  • Exception handling in async tasks (silent failures)
  • Debugging tools: asyncio debug mode, logging, breakpoints

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.