renderToNodeStream render function snippet - https://medium.com/homeaway-tech-blog/profiling-react-server-side-rendering-to-free-the-node-js-event-loop-7f0fe455a901

render.js

// https://medium.com/homeaway-tech-blog/profiling-react-server-side-rendering-to-free-the-node-js-event-loop-7f0fe455a901 
const ReactDOMServer = require('react-dom/server');
     
const render = (reactComponent) => { 
    return new Promise((resolve, reject) => { 
        const body = [];
        const bodyStream = ReactDOMServer.renderToNodeStream(reactComponent); 
        bodyStream.on('data', (chunk) => { 
            body.push(chunk.toString()); 
        }); 
        bodyStream.on('error', (err) => {
            reject(err); 
        });
        bodyStream.on('end', () => {   
            resolve(body.join('')); 
        });
    }); 
};
     
export default render;