unzip to s3.js

let path = require('path');
let aws = require('aws-sdk');
let s3Client = new aws.S3();
let zlib = require('zlib');
let s3s = require('s3-streams');

const output_bucket = "stackoverflow-bucket";

exports.handler = (event, context, callback) => {
    context.callbackWaitsForEmptyEventLoop = false;

    event.Records.forEach(record => {
        const params = {
            Bucket: record.s3.bucket.name,
            Key: record.s3.object.key
        };

        const isGzip = path.extname(params.Key) === ".gz";
        let readStream = s3Client.getObject(params).createReadStream();

        readStream = isGzip ? readStream.pipe(zlib.createGunzip()) : readStream;
        writeStream = s3s.WriteStream(s3Client, { Bucket: output_bucket, Key: path.basename(params.Key, ".gz") });

        // begins the actual streaming
        readStream.pipe(writeStream);

        writeStream.on('end', () => {
            callback(null, `Handled ${JSON.stringify(params)}`);
        });
    });
};

Sorry. That was a really stupid question. Found it here: http://docs.aws.amazon.com/lambda/latest/dg/nodejs-create-deployment-pkg.html