title: Unable to connect DB on over 200 concurrent request
body: <p>I'm using RDS from amazon, and tuned the MySQL config to the max.
  However, all the site will be stop connecting to the MySQL when the number of connection reached a certain numbers of activities. It's internal network setup, no bandwidth limit and 128GB RAM 32 core Windows Server 2019 Datacenter ECS instance.</p>
  <p>The following are my MPM, Httpd.conf, and PHP.ini
  Could it be causing by the following configuration?</p>
  <pre><code>MPM Configuration
  &lt;IfModule mpm_winnt_module&gt;
      ThreadLimit       2000000
      ThreadsPerChild   2000000
      MaxConnectionsPerChild 0
      MaxRequestsPerChild    0
  &lt;/IfModule&gt;
  
  HTTPD2.4 Configuration
  KeepAliveTimeout 180
  MaxKeepAliveRequests 10000
  Timeout 3200
  FcgidMaxRequestLen 51200000
  &lt;IfModule mpm_winnt_module&gt;
      MaxConnectionsPerChild 10000000
      ThreadsPerChild 1920
  &lt;/IfModule&gt;
  
  PHP7.0 Configuration
  max_execution_time = 1800
  max_input_time = 60
  memory_limit = 65536M
  </code></pre>
  <p>All calling from the same instance, sharing the same php file initiating the DB connection. Approx 20 connections sharing by 20 sites, opening 200 pages at the same time. The DB will refused the connection. The following is the setting of RDS
  innodb_io_capacity 18446744073709551615
  innodb_io_capacity_max 4294967295
  innodb_read_io_threads 64
  innodb_write_io_threads 64</p>
  <p>Single RDS instance with 20 DB instances.</p>
  <p>PHP code used to initiate the DB instance for site global usage.</p>
  <pre><code>$db1 = new MySQLi(&quot;mysql.abc.com&quot;,&quot;testing&quot;,&quot;abc#123&quot;,&quot;testing&quot;,3306);
  $db1-&gt;query(&quot;set names utf8&quot;);
  unset($db2);
  $db2 = new MySQLi(&quot;mysql.abc.com&quot;,&quot;testing&quot;,&quot;abc#123&quot;,&quot;testing&quot;,3306);
  $db2-&gt;query(&quot;set names utf8&quot;);
  </code></pre>