Flash sales are brutal stress tests for your Shopify store. You spend weeks building hype, send the email blast, and within 60 seconds — your site slows to a crawl. Checkouts time out. Customers leave. Revenue disappears. The frustrating part? Shopify's infrastructure is not the problem. The real culprits are things you control: Third-party app scripts loading on every page Unoptimized Liquid code blocking render Checkout flows never tested under concurrent load Inventory sync apps that fail when hit with simultaneous cart requests The Technical Breakdown When a flash sale goes live, here is what hits your store simultaneously: User lands on product page → CDN serves assets User adds to cart → Cart API call fires User hits checkout → Payment gateway + inventory check All of the above × 5,000 → Everything queues or fails Most stores fail at the checkout and inventory layer, not at the CDN level. What You Should Do Before Every Flash Sale Kill non-essential apps Every active app injects scripts.…