title: SequlizeJS connection get timeout frequently
body: <p>We have a project backend running on <strong>NodeJS</strong> / <strong>expressJS</strong> / <strong>SequilizeJS</strong> as a <strong>RESTapi</strong>.
  That <strong>RESTapi</strong> connceted to a <strong>VueJS</strong> SPA.</p>
  
  <p>Only 5 people use this system.
  Most of the operations are transactions.</p>
  
  <p>We get an error</p>
  
  <blockquote>
    <p>SequelizeConnectionAcquireTimeoutError: Operation timeout</p>
  </blockquote>
  
  <p>This is our config object.</p>
  
  <pre><code>const sequelize = new Sequelize(
    config.database,
    config.username,
    config.password,
    {
      host: config.host,
      dialect: "mysql",
      pool: {
        max: 20,
        min: 0,
        acquire: 30000,
        idle: 10000
      }
    }
  );
  </code></pre>
  
  <p>We are certain that our server's memory is not the issue. Because only 5 percent is used.</p>
  
  <p>Where does this error comes from?</p>