Nothing waits here
Shopify announces the order. QuickBooks accepts the write. No timer sits between them.
Shopify tells us about an order the moment it’s placed, and writing to QuickBooks takes under a second from there. That makes this one of the quieter pairs to run: no interval to sit behind, no gap between the sale and the entry. Compare a marketplace pair, where an Etsy order is looked for every five minutes and a busy hour can put a few sales a step behind.
Where the same-second write pays off is the second shop. Most people asking this question run Shopify and something else, an Etsy shop, an Amazon listing, a Square till, and the QuickBooks item is the one place all of them meet. If the quantity there is set from every shop as each sells, the books describe the shelf. If it’s set from one shop’s payout every few days, they describe the past.