Typical conversion rates hover around 3-4%. That is if 100 items were viewed, only 3-4 times they are bought. So, to decrease load on your sourcing engine, it m

Typical conversion rates hover around 3-4%. That is if 100 items were viewed, only 3-4 times they are bought. So, to decrease load on your sourcing engine, it makes sense to cache the "next 2 hours" calculation results and recalculate exactly during checkout.