The bug only surfaced when I demoed to the VP. A beautiful dark-grey screen, zero data, p

A demo to a VP failed because a hard-coded userId constant worked in production but broke in staging, where IDs were hashed into alphanumeric strings. The component expected digits, received letters, and rendered a blank screen. The fix was trivial—reading from an env var instead of hard-coding—but the lesson in always externalizing configuration was lasting.