Modified script

gistfile1.txt

const aws = require('aws-sdk');
var endpoint =  new AWS.Endpoint('https://search-arduino-test-ybrxss46t4wvvczoi5tipwrvz4.us-west-2.es.amazonaws.com');
exports.handler = function(event, context) {
    var req = new AWS.HttpRequest(endpoint);

    req.method = 'POST';
    req.path = path.join('/', esDomain.index, esDomain.doctype);
    req.region = esDomain.region;
    req.body = event;
    req.headers['presigned-expires'] = false;
    req.headers['Host'] = endpoint.host;

    // Sign the request (Sigv4)
    // var signer = new AWS.Signers.V4(req, 'es');
    // signer.addAuthorization(creds, new Date());

    // Post document to ES
    var send = new AWS.NodeHttpClient();
    send.handleRequest(req, null, function(httpResp) {
        var body = '';
        httpResp.on('data', function (chunk) {
            body += chunk;
        });
        
        httpResp.on('end', function (chunk) {
            console.log(body);
            context.succeed();
        });
    });
}