{
    "rules": {
      "messages": {
        ".read": true,
        // Users can only write messages if they are authenticated.
        ".write": "auth !== null",
        "$messageId": {
          // The name has to be the real display name.
          ".validate": "newData.child('name').val() === auth.token.name",
          "text": {
            // The text has to be less than 300 char.
            ".validate": "newData.isString() && newData.val().length < 300"
          }
        }
      },
      "fcmTokens": {
        // User can write their tokens to the database but not read the list of tokens.
        ".read": false,
        ".write": true
      }
    }
  }