Defrost, peel, devein, and remove the tails of the shrimp. Pat the shrimp dry, then drizzle with 2 teaspoons of olive oil and season with a pinch of salt.
Heat a large sauté pan or skillet over medium heat. Once hot, add the butter and Calabrian chilis. When the butter has melted, add the shrimp. Cook for 3–5 minutes, depending on their size, flipping midway, until just cooked through. Remove the shrimp from the pan and set aside.
Reduce the heat to medium-low and add the garlic. Season with a pinch of salt and cook for 2–3 minutes, stirring frequently. Add the pastina and toast for another 2 minutes, stirring constantly to prevent the garlic from burning.
Pour in the broth and lemon juice, then stir to combine. Cover the pot with a lid and cook, stirring every few minutes, until the pastina has absorbed most of the broth and the pasta is al dente. Cooking time may vary from the package instructions, but this should take about 15–20 minutes.
Add the shrimp back in, with the cilantro and mix to incorporate. Serve immediately.