In a medium mixing bowl, combine mayonnaise, sour cream, the zest of one lime, and the juice of that lime. Add Dijon mustard, minced garlic, freshly chopped dill, and kosher salt. Mix well until smooth and creamy, then set aside.

Bring a pot of salted water to a boil. Add shrimp and cook for 2-3 minutes until pink and opaque. Remove and drain briefly in a colander.

Transfer the cooked shrimp to a bowl with ice water for 3-5 minutes to cool.

Pat the shrimp dry and chop into bite-sized pieces. In a large mixing bowl, add diced cucumber and sliced green onions. Toss in chopped shrimp, then pour the creamy dressing over the mixture.

Gently fold the cucumber, shrimp, and dressing together until well-coated. Avoid mashing the ingredients.

Serve immediately for optimal freshness, either on a bed of lettuce or directly from the bowl.