In a large bowl, combine the shrimp with baking soda, kosher salt, and Old Bay Seasoning. Allow to sit for 15-20 minutes.

While the shrimp is brining, fill another large bowl with cold water and ice for an ice bath.

Bring a medium pot of water to a gentle boil, add fresh lemon juice, then poach the brined shrimp for 90 seconds until pink and opaque.

Transfer the poached shrimp to the ice bath immediately and let cool for about 5 minutes.

In a mixing bowl, whisk together mayonnaise, Dijon mustard, lemon juice, dill, Old Bay Seasoning, celery seed, salt, and pepper.

Fold in chopped celery and red onion into the dressing.

Gently fold the cooled shrimp into the dressing mixture, ensuring even coating.

Cover and refrigerate the salad for at least 2 hours or overnight to enhance flavor.