Boil soba noodles as per package instructions, then drain and rinse under cold water.
In a bowl, whisk together rice vinegar, soy sauce, lime zest and juice, sesame oil, brown sugar, garlic, and red pepper flakes.
Grate the carrots and roughly chop the cilantro and peanuts.
In a large bowl, combine noodles, carrots, and cilantro.
Pour the dressing over the salad and toss gently to coat everything evenly.
Top with chopped peanuts and an extra squeeze of lime if desired.
Chill for 15 minutes for best flavor, or serve immediately.
Store leftovers in an airtight container in the fridge—great for next-day lunches!