Peel and devein shrimps: remove the shrimp head. Remove the outer shell. Finally, remove the vein. You can do that using a toothpick. Pat dry the shrimps before the next step.
Prepare the coating station: Add buttermilk in one bowl and season with a pinch of salt. In a separate bowl, combine tapioca starch or cornstarch with salt and pepper, to taste.
Coat the shrimp with buttermilk and allow the excess liquid to drip. Coat the shrimp with tapioca starch and gently shake off the excess.
Fry the shrimps; heat 4-inches of oil in a saucepan over medium-high heat. Carefully add shrimp to the heated oil. Fry the shrimp for 1-2 minutes per side and transfer onto the wire rack lined with paper towels. Do not overcrowd the pot and if needed do this in batches.
Prepare the sauce:
Make your sauce: combine mayonnaise, sweet chili sauce, Sriracha, and salt to taste in a bowl.
Serve the shrimps:
Serve shrimp warm with the sauce on the side.
Notes
Fry the shrimps in batches. Overcrowding the pan will lower the oil temperature. This will make your shrimps soggy.