In a large bowl, soak the shrimp in buttermilk for at least 30 minutes.
In another bowl, combine flour, garlic powder, paprika, cayenne pepper, salt, and black pepper. Mix well.
In a third bowl, place the panko breadcrumbs.
Remove the shrimp from the buttermilk, allowing excess to drip off. Dredge each shrimp in the flour mixture, shaking off the excess, then dip into the panko breadcrumbs, pressing gently to adhere.
In a large skillet, heat about 1 inch of vegetable oil over medium-high heat. Once hot, carefully add the shrimp in batches, being careful not to overcrowd the pan.
Fry until golden brown and crispy, about 2-3 minutes per side. Remove and drain on paper towels.
For the Boom Boom Sauce, whisk together mayonnaise, sweet chili sauce, sriracha, and lime juice in a small bowl until smooth.
Serve the crispy shrimp hot with the Boom Boom Sauce on the side for dipping.