Combine the olive oil, vinegar, mustard, salt, and pepper in a jar with a tight-fitting lid. Shake well to combine.
Meanwhile, heat a large pot of water over high heat until boiling. Season generously with salt. Add the green beans and cook for 3 to 5 minutes, until tender, yet still a little crisp. Transfer the cooked beans to a bowl of ice water. Let sit 3 minutes to cool, then drain.
Combine the green beans, red onion, tomato, olives, and dressing in a large mixing bowl. Gently fold together so that the dressing coats the vegetables. Season with more salt and pepper to taste.
Transfer to a platter and top with goat cheese and almonds, if you like.
