Combine mayonnaise, sour cream, lime zest and juice, dill, Dijon mustard, minced garlic, kosher salt, and a pinch of pepper in a bowl; mix thoroughly and chill.
Bring a large pot of water to a rolling boil.
Add the shrimp to the boiling water and cook just until they turn pink and are opaque, about 2 to 3 minutes.
Prepare a large bowl of ice water while shrimp are cooking.
Using a slotted spoon, transfer the cooked shrimp into the ice water to stop the cooking and cool completely; leave for 3 minutes.
Drain the shrimp well and cut into bite-sized pieces.
In a mixing bowl, combine chopped shrimp, diced cucumber, sliced green onions, and the chilled dressing.
Gently toss everything together until all ingredients are evenly coated with the creamy lime dressing.
Serve immediately or refrigerate until ready to enjoy.
