In a large bowl, combine the cornstarch, flour, salt, black pepper, garlic powder, onion powder, and cayenne pepper. Mix well to create the coating.

Pat the shrimp dry with paper towels to remove excess moisture. This helps achieve a crispier texture.

Toss the shrimp in the coating mixture until evenly coated. Shake off any excess flour.

In a large skillet or deep frying pan, heat about 1 inch of vegetable oil over medium-high heat until it reaches 350°F.

Carefully add the shrimp to the hot oil in batches, making sure not to overcrowd the pan. Fry for 2-3 minutes or until golden brown and crispy. Remove with a slotted spoon and drain on paper towels.

Repeat with the remaining shrimp, adjusting the heat as necessary to maintain the oil temperature.

Once all the shrimp are cooked, transfer them to a serving platter, garnish with sliced green onions, and serve with lemon wedges on the side.