Monitor the funnel, not just the homepage
A homepage check tells you the site is serving traffic. It tells you nothing about whether anyone can actually buy something. The failure modes that cost money live deeper in the funnel, on pages that are harder to reach and therefore less frequently checked.
Every step from product page to cart to checkout to payment confirmation deserves its own monitor, because each one can fail independently while the others look fine.
Search returning nothing is an outage
Site search is the clearest example of a soft failure. When the search index is broken or empty, the endpoint returns HTTP 200 with an empty result set. Every conventional uptime monitor reports the site as perfectly healthy.
Meanwhile, every customer who searches sees no products and leaves. A body assertion requiring a known result is what turns this from an invisible revenue leak into an alert.
Get ready before the peak, not during it
The week before a major sale is when monitoring coverage should be reviewed and tightened, not the morning of. Increase check frequency on revenue paths, verify alert routing reaches someone who will be awake, and confirm your status page is reachable and up to date.
It is also worth checking that certificate expiry dates do not fall inside your peak window — a surprising number of seasonal outages are just a certificate that lapsed on the worst possible weekend.