Peel the cucumbers if desired, then thinly slice them using a mandoline slicer for even slices.

Place the sliced cucumbers in a colander and sprinkle with salt. Allow them to sit for about 10 minutes to release excess water, then pat them dry with paper towels.

In a large mixing bowl, combine the cucumbers, red onion, cilantro, and roasted peanuts. If desired, add the sliced red chili for spice.

In a separate small bowl, whisk together the rice vinegar, sugar, soy sauce, sesame oil, salt, and black pepper until the sugar is fully dissolved.

Pour the dressing over the cucumber mixture and toss gently to combine, ensuring everything is well-coated.

Let the salad marinate in the refrigerator for at least 15 minutes before serving to allow the flavors to meld.

Serve cold as a refreshing side dish or light appetizer.