Bring 8 cups of generously salted water to a boil in a large pot.
While the water boils, prepare the shrimp. Heat the oil in a large nonstick pan over medium-high heat. Add the shrimp and garlic and cook, turning when the first side is pink. Cook until the second side is pink as well, about 3 minutes total. Transfer the shrimp to a bowl and set aside. Do not clean the pan.
Add the cream cheese, parmesan, water, and red pepper flakes to the now empty pan along with any juices remaining from the shrimp. Bring to a simmer, whisking to obtain a smooth sauce. Remove from heat and stir in lemon zest and juice.
Add pasta to the boiling water and stir to separate the noodles. Cook until al dente, about 3 to 5 minutes.
Add back the shrimp and the raw peas to the sauce and toss to coat. When the noodles are cooked, drain and add to the pan with the sauce and shrimp. Toss to coat evenly, adding more water if needed. Serve with more parmesan, if desired.