Heroku build failing node.js - mysql

Question

My dev build was working fine but I can't understand why the deploy is failing.
Using ClearDB add on for MySQL, but I can't tell if the database connection is the problem here as the log output is "Connected".
Log:
-----> Build
Running heroku-postbuild
> react-notes-app#0.1.0 heroku-postbuild /tmp/build_8b518789_
> node api/server.js
Warning: connect.session() MemoryStore is not
designed for a production environment, as it will leak
memory, and will not scale past a single process.
Connected!
-----> Timed out running buildpack Node.js
Terminated
! Push failed
db.js:
const mysql = require('mysql');
var con = mysql.createPool(db_config);
con.getConnection(function(err) {
if (err) throw err;
console.log("Connected!");
});
//some functions
server.js:
const express = require('express');
const app = express();
const bodyParser = require('body-parser');
const session = require('express-session');
const PORT = 5000 || process.env.port;
const cors = require('cors');
const path = require('path');
const db = require('./db.js');
var md5 = require('md5');
app.use(express.static(path.join(__dirname, '../build')));
app.use(cors());
app.get('/', function(req,res) {
res.sendFile(path.join(__dirname, '../build', 'index.html'));
});
//other stuff
Read answers to similar posts and some have problems in their dependencies.
package.json:
{
"name": "react-notes-app",
"version": "0.1.0",
"private": true,
"dependencies": {
"#testing-library/jest-dom": "^4.2.4",
"#testing-library/react": "^9.5.0",
"#testing-library/user-event": "^7.2.1",
"cors": "^2.8.5",
"express-session": "^1.17.1",
"md5": "^2.3.0",
"mysql": "^2.18.1",
"node-fetch": "^2.6.0",
"react": "^16.13.1",
"react-dom": "^16.13.1",
"react-scripts": "3.4.3"
},
"proxy" : "https://reactnote-app.herokuapp.com",
"scripts": {
"start": "react-scripts start",
"test": "react-scripts test",
"eject": "react-scripts eject",
"heroku-postbuild": "node api/server.js"
},
"eslintConfig": {
"extends": "react-app"
},
"browserslist": {
"production": [
">0.2%",
"not dead",
"not op_mini all"
],
"development": [
"last 1 chrome version",
"last 1 firefox version",
"last 1 safari version"
]
},
"engines":{
"node":"v12.18.3",
"npm":"6.14.6"
}
}