Bring a large pot of salted water to a boil. Add the pasta and cook until just al dente, about 1-2 minutes less than package instructions. Drain, reserving a cup of pasta water, and set aside.
While the pasta cooks, heat olive oil in a large skillet over medium-high heat. Once shimmering, add the sliced garlic and cook for about 30 seconds until fragrant and lightly golden, stirring constantly to prevent burning.
Sprinkle the chili flakes into the oil and garlic, stirring quickly until the flakes shimmer and release smoky aroma, about 10 seconds. Immediately add the raw shrimp, seasoning with salt and pepper.
Sear the shrimp for 1-2 minutes per side until they turn bright pink and are just cooked through. Use a slotted spoon to transfer the shrimp to a plate if they finish early, leaving the flavorful oil and garlic in the skillet.
Add the cooked pasta to the skillet with the garlic and chili oil. Pour in a splash of the reserved pasta water and toss vigorously to coat the noodles evenly, allowing the sauce to loosen and cling to everything.
Squeeze fresh lemon juice over the pasta and stir to combine, brightening the flavor. Taste and adjust seasoning with more salt, pepper, or chili flakes if desired.
Return the cooked shrimp to the skillet, tossing again to combine. Let everything sit for a minute to meld flavors, then transfer to plates and serve immediately, garnished with fresh herbs if desired.
