When pages take too long.
WHAT TO ESTABLISH FIRST
Whether it is all pages or some Whether it affects logged-in users differently Whether it started recently
ALL PAGES SLOW
Usually no caching, an old PHP version, or a heavy theme.
SOME PAGES SLOW
Something on those pages: a query, an external request, a heavy plugin.
LOGGED-IN SLOW, LOGGED-OUT FAST
Caching is working for visitors and not for you.
That is expected behaviour, and it means the underlying site is slow.
EXTERNAL REQUESTS
A page calling another server waits for it.
If that server is slow, your page is slow.
Common with social feeds, external APIs and remote fonts.
HOW TO FIND IT
A query-monitoring plugin shows what runs and how long it takes.
Use it on a staging copy where possible.
WHAT TO DO WITH FINDINGS
Identify the component. Frequently the answer is to remove or replace it.
