database.rules.json

{
  "rules": {
    "event": {
      ".read": true,
      "$event_id": {
        ".write": "newData.exists() || auth.id === 'not-a-real-key'",
        "eventname": {
          ".write": "!data.exists() && newData.exists()",
          ".validate": "newData.isString() && newData.val().length <=100"
        },
        "eventLocation": {
          ".write": "!data.exists()",
          ".validate": "newData.isString() && newData.val().length <=100"
        },
        "eventDesc": {
          ".write": "!data.exists()",
          ".validate": "newData.isString() && newData.val().length <=100"
        },
        "hostName": {
          ".write": "!data.exists()",
          ".validate": "newData.isString() && newData.val().length <=100"
        },
        "hostEmail": {
          ".write": "true",
          ".validate": "newData.val().length <=100"
        },
        "dates": {
          "$date": { "participants": { ".write": "newData.exists()" } }
        },
        "admin": {
          ".write": "!data.exists()",
          ".validate": "newData.isString() && newData.val().length <=100"
        },
        "created": {
          ".write": "!data.exists()",
          ".validate": "newData.isNumber() && newData.val()<1000000000000"
        },
        "deleteAt": {
          ".write": "newData.exists() && (newData.val()< data.val() || !data.exists())",
          ".validate": "newData.isNumber() && newData.val()<1000000000000"
        },
        "active": {
          ".write": "!data.exists()",
          ".validate": "newData.isBoolean()"
        },
        "$other": { ".validate": false }
      },
      ".indexOn": ["admin", "deleteAt"]
    }
  }
}