Memory quota exceeded when deploying to Heroku

Building on local machine works fine, and takes about 10 seconds, but fails once deployed to Heroku. 2 out of 10 times it success building production build on Heroku, i don’t know why.

2018-10-15T19:32:06.251040+00:00 heroku[web.1]: Starting process with command `npm run build && node app.js`
2018-10-15T19:32:09.573768+00:00 app[web.1]: 
2018-10-15T19:32:09.573787+00:00 app[web.1]: > react-app@0.1.0 build /app
2018-10-15T19:32:09.573789+00:00 app[web.1]: > react-scripts build
2018-10-15T19:32:09.573791+00:00 app[web.1]: 
2018-10-15T19:32:14.133886+00:00 app[web.1]: Creating an optimized production build...
2018-10-15T19:32:41.548599+00:00 heroku[web.1]: Process running mem=600M(117.4%)
2018-10-15T19:32:41.548726+00:00 heroku[web.1]: Error R14 (Memory quota exceeded)
2018-10-15T19:33:06.390664+00:00 heroku[web.1]: Error R10 (Boot timeout) -> Web process failed to bind to $PORT within 60 seconds of launch
2018-10-15T19:33:06.390664+00:00 heroku[web.1]: Stopping process with SIGKILL
2018-10-15T19:33:06.541622+00:00 heroku[web.1]: Process exited with status 137
2018-10-15T19:33:06.561336+00:00 heroku[web.1]: State changed from starting to crashed
2018-10-15T19:33:06.563135+00:00 heroku[web.1]: State changed from crashed to starting
2018-10-15T19:33:24.413153+00:00 heroku[web.1]: Starting process with command `npm run build && node app.js`

My app.js example

const express = require('express');
const http = require('http');
const path = require('path');
let app = express();

app.use(express.static(path.join(__dirname, 'build')));
const port = process.env.PORT || '3000';
app.set('port', port);
const server = http.createServer(app);
server.listen(port, '0.0.0.0', () => console.log(`Running on localhost:${port}`));

Procfile

web: npm run build && node app.js

[Timer]

But yes, the proper solution is building in postinstall. Better yet, use the heroku-postbuild so this only happens in Heroku.

[Keksike]

Workaround for me is to add "postinstall": "react-scripts build" to package.json in scripts, but question is still open

If I have understood correctly, this isn’t a workaround, but rather the correct way of doing it. The building should be done on postinstall or heroku-postbuild rather than start.