Once you plate a Shrimp Louie Salad, it is best to finish it. However, you can prepare each of the components in advance and store them in separate airtight containers in the fridge.
While you may love the newer version with shrimp, the original Louie (or Louis) salad is a crab dish that seems to have originated on the West Coast sometime in the late 19th or early 20th centuries.