Complimenten over zang en kei goed optreden

What does “kei goed” mean in Flemish Dutch?

In Flemish Dutch, kei is the standard teen intensifier. Kei goed = “really good,” kei tof = “really cool,” kei lekker = “really tasty.” It comes from kei (literally “boulder, big stone”) used adjectivally, like English “rock-solid” sliding into “really.” Standard Dutch (NL) doesn’t use it; Dutch teens reach for super, vet, or lekker. In Flanders the word is everywhere. Older Belgians sometimes complain about its overuse; it sticks anyway.

In this Play audition clip, the coach gives a singer the final verdict on her performance: “Is kei goed.”