In a mixing bowl, combine mayonnaise, sour cream, lime zest, lime juice, dill, Dijon mustard, minced garlic, kosher salt, and black pepper. Whisk until smooth and creamy. Chill for at least 30 minutes.

Bring a pot of water to a rolling boil. Add shrimp and cook for 2-3 minutes until they turn pink. Remove from heat.

Prepare an ice water bath. Transfer boiled shrimp to the ice water for 3 minutes. Drain well.

In a large bowl, combine the chilled shrimp, diced cucumber, and sliced green onions. Toss gently. Add the chilled dressing and stir until coated.