What to cache and what not to.
WHAT MUST NOT BE CACHED
Cart Checkout My account Any page showing per-customer content
WHY
A cached cart shows one customer another's items, or an empty cart.
WHAT HAPPENS IF YOU GET IT WRONG
Customers report vanishing carts, wrong totals, or someone else's details.
Alarming, and entirely a caching misconfiguration.
HOW TO SET IT UP
Most caching plugins exclude shop pages automatically.
Verify rather than assuming.
WHAT TO CACHE
Product pages Category pages Content pages
Those are most of your traffic.
FOR LOGGED-IN CUSTOMERS
Usually not cached, so the underlying site speed matters for them.
AFTER CONFIGURING
Test as a guest, in a private window: add to cart, view cart, checkout.
Then test again logged in.
WHAT TO RECHECK
After any caching plugin update.
