Table of Contents
Async Python is not just sync Python with async/await sprinkled on top. It requires a different mental model for concurrency, error handling, and resource management. Many Python developers claim async experience but have never built a production async system. Here's what actually matters.
Core Async Concepts Every Engineer Must Know
Production Async Knowledge
- ✦ Distributed tracing and observability
- ✦ Rate limiting and backpressure handling
- ✦ Circuit breaker implementation
- ✦ Graceful shutdown procedures
- ✦ Memory leak investigation
- ✦ Concurrency-safe resource management
Must-Have Skills
Beyond syntax:
- ✦ Experience with async database drivers (asyncpg, aiosqlite, motor for MongoDB)
- ✦ Async HTTP clients (httpx, aiohttp) vs sync requests
- ✦ Background task management (asyncio.create_task, BackgroundTasks)
- ✦ Handling task cancellation properly
- ✦ Resource cleanup with async context managers
Testing Async Code
Sign of seniority:
- ✦ pytest-asyncio or similar for testing coroutines
- ✦ Mocking async functions (AsyncMock)
- ✦ Testing timeout and cancellation behavior
- ✦ Testing concurrent execution paths
Production Scenarios to Discuss
Investigate event loop blocking, connection pool exhaustion, database latency, and external dependency performance.
Apply timeouts, retries with limits, circuit breakers, and fallback behavior.
Interview Questions
gather returns results when all complete. wait returns when any/first complete. gather raises exceptions immediately; wait returns done/pending sets.
asyncio.wait_for or async with asyncio.timeout(delay). Handle TimeoutError appropriately.
Exception is stored in the task and raised when task.result() is called. Use asyncio.gather(return_exceptions=True) or add_done_callback.
Signals of Senior Async Engineers
- ✦ Has handled production incidents involving async systems
- ✦ Can explain tradeoffs of concurrency models
- ✦ Understands observability and tracing
- ✦ Has experience scaling APIs under real traffic
- ✦ Can mentor teams on async architecture decisions
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