Much Applied

Most recipes can yield enough to feed a village. OK, that is a bit of an exaggeration, but still, if it is your first time making it and your village consists of just you and your better half, a bad result becomes an abusive diet to your loved one, or an abuse to the environment through huge waste. Even if it was a good result, the huge quantity lasts for days and you end up feeling sick of it.

A lot of recipes are probably passed down from many generations ago when a household commonly was as large as a village.

If it was a meat dish, you probably can freeze the leftovers. Freezing detracts from the quality of most food, not just the taste and nutrition, but especially the texture. Anyway, it is (loosely) viable. When it is Carbonara, you are eating it, the whole lot of it, that very meal! No matter how yummy it is, which it was, as I struck beginner's luck, there is a limit to the size of your stomach.

It is often difficult to scale a recipe and keep the recipe-intended quality at the same time.

The good news is that if you got all the basic skills down, and you have learned from wide enough range of recipes, you can spot the pattern and understand which basic building blocks are used in the recipe. Then, you can scale down the recipe by your experience. In the case of Carbonara, it is essentially the same concept as making custard with whole eggs, except the liquid is the pasta cooking water, it is savory instead of sweet, and cheese is added. 

Boy, it has been a long fattening road. But I am glad that the experiences are starting to pay off. I think, life is funny. No experience ever goes to waste, no matter how bad or useless they may seem at the time. They always serve us later, even if it is in small ways.

tip: 

Here is a general egg to liquid proportion reference for custard: http://www.incredibleegg.org/eggcyclopedia/c/custard/

I think the quarter cup to one egg ratio, with the cheese, gave a nice thick but not stiff sauce in Carbonara. However, as you don't want to drain the pasta for too long and allow it to lose too much heat, it will retain some cooking water. You may want to start with just 1 tablespoon of hot pasta water for each egg first and add more as needed.