Bring a large pot of salted water to a rolling boil. Add the shrimp and cook for 2-3 minutes until they turn pink and curl slightly. The moment they're done, drain and immediately plunge them into an ice bath. This stops the cooking process and keeps them tender rather than rubbery. Pat completely dry with paper towels.

In a large mixing bowl, whisk together mayonnaise, fresh lemon juice, and Dijon mustard until smooth and creamy. Taste and adjust the acidity to your family's preference.

Add the chopped celery, minced red onion, fresh dill, and capers to the dressing. Let this mixture sit for a few minutes to allow the flavors to meld.

Gently fold the cooled shrimp into the vegetable and dressing mixture. Be careful not to overmix, as you want to maintain the shrimp's shape and texture. Season with salt and freshly ground black pepper.

Refrigerate for at least 30 minutes before serving. This chilling time allows all the flavors to marry together beautifully. Serve over a bed of mixed greens for a complete meal.