Sweet and Sour Glazed Shrimp

Name: Sweet and Sour Glazed Shrimp
Ingredients: 1/4 cup Chinese plum sauce; 1/4 cup ketchup; 2 teaspoons soy sauce; 1/4 teaspoon crushed red pepper flakes; 1 1/4 pounds medium shrimp, peeled and deveined and tails removed; Kosher salt and freshly ground black pepper; 1 tablespoon peanut oil; 2 scallions, thinly sliced (white and green parts kept separate); 1 clove garlic, finely chopped; 1 teaspoon finely chopped peeled fresh ginger; 3 tablespoons unseasoned rice wine vinegar; Cooked white rice, for serving, optional