In a mixing bowl, combine mayonnaise, sour cream, lime zest, lime juice, dill, mustard, and salt.

Bring a large pot of water to a gentle boil. Add shrimp and cook for 2-3 minutes until pink and opaque.

Transfer cooked shrimp to a bowl of ice water for 3 minutes, then drain and chop.

Slice cucumber and chop green onions while shrimp chill.

Combine chopped shrimp, cucumber, and green onions in a bowl. Add dressing and fold gently.

Serve immediately in lettuce wraps or on its own, optionally garnish with dill.