Pat dry: Lay the peeled shrimp on a plate lined with paper towels. Place another layer of paper towels on top and press gently to absorb moisture. Remove the top layer, sprinkle the shrimp with the salt, and let them sit uncovered at room temperature for 15 minutes. This draws out more moisture from the surface.
Season: Transfer the shrimp to a large bowl. Add the cornstarch, garlic powder, smoked paprika, and cayenne (if using). Toss gently with your hands or a spatula until every shrimp is evenly coated in a thin, dusty layer.
Add oil: Drizzle the oil over the seasoned shrimp and toss again. The cornstarch will absorb the oil slightly, creating a thin paste-like coating that clings to the shrimp and crisps beautifully.
Preheat: Preheat your air fryer to 400°F for 3 minutes. A hot start is essential for immediate crispiness.
Arrange: Place the shrimp in a single layer in the air fryer basket. Leave a little space between each one — if they're touching, they'll steam instead of crisp. Work in batches if needed.
Cook: Air fry at 400°F for 5–7 minutes, shaking the basket gently halfway through. At the 5-minute mark, check for doneness. The shrimp should be pink and opaque, and the coating should be golden and firm to the touch.
Rest: Remove the shrimp from the basket immediately and transfer to a wire rack set over a baking sheet (or a clean plate lined with a fresh paper towel). This keeps the bottoms from steaming. Let them rest for 1-2 minutes before serving.