In a medium bowl, whisk together mayonnaise, Dijon mustard, and apple cider vinegar until completely smooth and well combined.
Add the sweet pickle relish, celery seed, paprika, salt, and black pepper to the bowl.
Stir everything together until all ingredients are evenly distributed throughout the dressing.
Taste the dressing and adjust seasoning if needed—you might want more salt, pepper, or vinegar depending on your preference.
Let the dressing sit at room temperature for at least 15 minutes to allow the flavors to meld together.
When ready to use, pour the dressing over 3 pounds of cooled, cooked potatoes (cut into bite-sized pieces) in a large bowl.
Gently toss the potatoes with the dressing until all pieces are evenly coated.
Serve immediately or refrigerate until ready to serve.
