A long and storied history of nasty surprises has taught me to never underestimate the complexity of an unfamiliar domain.

In that sense I'm surprised it's only 40,000.

Yeah, I'm pessimistically sure that there is other stuff, like:

* Checking whether each item scanned has satisfied a logical contract for a discount, some of which may be per-region, per-store, or even per-customer.

* If multiple exclusive coupons or deals are available, resolve the contradiction, preferably in favor of the customer.

* Check if any items or quantities of items require an ID to be shown before proceeding, and record information about the employee authorizing it.

* Update customer "rewards" data and generate any special offers so that you can put it onto their receipt.

And that's not even starting to get into all the other less-customer-synchronous stuff that you still need CPU power somewhere to do. Managing stock levels, orders, deliveries, price changes, anti-"shrinkage", employee shifts, market-research, status and repairs of freezer-units, operational logging and telemetry, every form of reporting/dashboard "strategic insight" stuff beloved by upper management...