Bring a large pot of salted water to a rolling boil. Add the fettuccine pasta and cook according to package instructions until al dente. Reserve ½ cup of pasta water, then drain the pasta and set aside.

In a large skillet, heat olive oil over medium heat. Add shrimp, season with salt, pepper, and optional red pepper flakes. Cook until shrimp are pink and opaque, about 2-3 minutes on each side. Remove from skillet.

In the same skillet, add minced garlic and sauté for about 1 minute. Pour in heavy cream and bring to a gentle simmer, cooking for 2-3 minutes.

Gradually whisk in Parmesan cheese until melted and smooth. Adjust consistency with reserved pasta water as needed, and season to taste.

Combine fettuccine and shrimp with the Alfredo sauce, tossing gently. Serve immediately, garnished with parsley.