Gist for the article -- https://medium.com/evenbit/making-a-firebase-server-worker-in-the-cloud-c46c37cc88f3

visits.bolt

path /visits/{visit_id} is Visit {
  read() { canManageBusiness(this.businessId) }
  write() { canManageBusiness(this.businessId) }
}

path /businessVisits/{business_id}/{visit_id} is Visit {
  read() { canManageBusiness(business_id) }
}

path /memberVisits/{member_id}/{visit_id} is Visit {
  read() { canManageBusiness(this.businessId) }
}

type Visit {
  duration: UnsignedNumber | Null,
  in: UnsignedNumber,
  memberId: String,
  out: UnsignedNumber | Null,
  businessId: String,

  validate() {
    (this.out === null || this.duration === (this.out - this.in))
  }
}

type UnsignedNumber extends Number {
  validate() { this >= 0 }
}

isSignedIn() { auth !== null }
isCurrentUser(uid) { isSignedIn() && auth.uid === uid }
canManageBusiness(id) {
  // Check that the user has proper credentials in your own logic
  isSignedIn()
}