Wiktionary
a. (context idiomatic English) Exactly what is necessary or useful in a given situation; something very beneficial or desirable.
Usage examples of "just what the doctor ordered".
A twenty- or thirty-minute soak before we have to head back is just what the doctor ordered after that damned ride.
A good lay was just what the doctor ordered, and so far this looked like it was going to turn out to be a good lay.
I think a Screaming Meemie unit is just what the doctor ordered, over.
But they say she's just what the doctor ordered, and the Duchess needs a lot of doctoring.
We're fast and we're smart and we are just what the doctor ordered.
He went scrambling for it without realizing how desperately he needed it,, trying to convince himself that it might be just the ticket, just what the doctor ordered.
He may not need one at that spot on the way out, but it might be just what the doctor ordered on the way back.
Everyone grumbled goodnaturedly and admitted that it was fun for the kiddies and that a touch of snow around Christmas was just what the doctor ordered.