Stop treating vendor day like a guess. Vendor Day Panic Rehearsal is a free, fast-read ebook that helps Shopify founders stabilize the order path before ad spend outruns fulfillment. In under an hour, you’ll map the real handoffs behind checkout, find the first bottleneck, and spot the warning signs that usually show up before late shipments, manual re-entry, and packing-table chaos. It is built to give you a clean, practical reset before your next promo so growth lands smoothly instead of creating a backlog. If your orders are rising faster than picking, packing, and shipping can keep up, this guide shows you where to tighten the system first and what to review before the week breaks.