Espresso is like the “heart” of coffee drinks. From the liquidated coffee called espresso as a base, you can add milk, sugar, ice, and other flavors to make hundreds of various coffee drinks.
Of course, you are the best judge for your coffee. If it makes you happy, the drink is good for you. However, if you are curious about the technical specifications of a standard cup of espresso, I will introduce you to a few from the set of parameters issued by the Italian Espresso National Institute to define a “Certified Espresso”. According to these standards, they are:
Necessary portion of ground coffee 7 g ± 0,5
Exit temperature of water from the unit 88°C ± 2°C
Temperature of the drink in the cup 67°C ± 3°C
Entry water pressure 9 bar ± 1
Percolation time 25 seconds ± 5 seconds
Viscosity at 45°C > 1,5 mPa s
Total fat > 2 mg/ml
Caffeine < 100 mg/cup
Milliliters in the cup (including froth) 25 ml ± 2,5

To make good espresso, you need more than a machine. The quality of beans, its roast profile, its freshness, and even the water quality contributes a great deal to your cup of espresso.
One important condition that contributes to the quality of an espresso is crema, the layer of foam found on the surface of a shot of espresso coffee. Naturally, Robusta beans deliver thick crema and that makes espresso lovers happy.