When Profiling Turns Into a Reality Check

Yesterday I finally deployed my micro‑service stack to production, only to see user reports of sudden latency spikes and error 429 flood. The fix didn’t come from a new library or a hot‑reload, it came from a simple “hand‑off” I had ignored while building the app. In development I ran a single instance on my laptop, so my database pool size, cache eviction policies, and HTTP client retries were set for perfect local performance. In a real, horizontally‑scalable environment these same hard‑coded