How long of propagation from k8s to kong

We are currently creating KongConsumer and KongCredential custom resources in k8s and wait for them to be synced via Ingress Controller to Kong.

However it would take times for the resources to be picked up by Kong and take effective. From seconds to 15 minutes as per our tests.

Can we have more details on how the sync process does and why it takes so unpredictable time.