database.rules.json

{
  "rules": {
    ".read": true,
    ".write": false,
    "ratings": {
      ".read": false,
      ".write": false,
      "$uid": {
        ".read": "auth.uid === $uid",
        ".write": "auth.uid === $uid"
      }
    },
    "featuredSessions": {
      ".read": false,
      ".write": false,
      "$uid": {
        ".read": "auth.uid === $uid",
        ".write": "auth.uid === $uid"
      }
    },
    "speakers": {
      ".read": true,
      ".write": "root.child('users').child(auth.uid).child('rules').child('speakers').val() === true"
    },
    "subscribers": {
      ".read": false,
      ".write": true
    },
    "notifications": {
      ".read": false,
      ".write": false,
      "subscribers": {
        ".read": true,
        ".write": true
      },
      "users": {
        ".read": false,
        ".write": false,
        "$uid": {
          ".read": "auth.uid === $uid",
          ".write": "auth.uid === $uid"
        }
      }
    }
  }
}