In a large pot, cook soba noodles according to packet directions. Drain, rinse noodles with cold water and set aside.
Pour into a large bowl the sesame oil, rice vinegar, soy sauce and lime juice. Mix in lime zest, brown sugar, garlic and chilli flakes; stir until sugar dissolves. Toss in carrots, peanuts and coriander.
Stir noodles into dressing mixture. Cover and refrigerate at least 1 hour.
Toss salad again before serving. If dry, splash with soy sauce and vinegar. Serve cold.