Japanese Potato Salad With Cucumbers, Carrots, and Red Onion

Ingredients

• pounds russet potatoes, about 3 large potatoes, peeled and quartered
• Kosher salt
• Persian cucumbers, thinly sliced crosswise
• teaspoons rice wine vinegar
• tablespoons homemade or store-bought Japanese mayonnaise, such as Kewpie
• teaspoon Japanese hot mustard
• small carrot, quartered and thinly sliced crosswise
• red onion, thinly sliced
• hard boiled eggs , chopped
• scallion, white and light green parts only, chopped