Why it fixes most resource problems.
WHAT IT DOES
Serves a stored copy instead of building the page.
WHAT THAT REMOVES
PHP execution Database queries Most memory use Most processor use
For a cached response, nearly all of it.
WHY IT ADDRESSES EVERY LIMIT AT ONCE
Fewer entry processes, since responses are faster Less processor, since nothing is built Less memory, since PHP is not involved Fewer disk reads, since the database is not queried
WHAT IT DOES NOT HELP
Logged-in traffic, which is usually not cached Cart and checkout pages Admin activity
FOR A SHOP
Product and category pages cache. Cart and checkout do not.
That makes the rest matter more.
HOW TO SET IT UP
A caching plugin. Configure, clear, test logged out.
WHAT TO VERIFY
That caching is actually active.
Many sites have a caching plugin installed and not working.
WHERE TO START
This, before anything else.
