3 Hours Wasted on asyncio Pitfalls That Almost Took Down Production

Last Friday at 5 PM, right when I was about to close my laptop and sneak out, the alert channel exploded — the online data collection service had a timeout rate spiking to 40%, and all downstream reports were blank. I checked the logs and found that the crawler processing thousands of URLs was still using the old synchronous requests library, fetching them one by one. Each request averaged 1.2 seconds, one full round took nearly 20 minutes, but the business requirement demanded completion within