Running Mirth Channel with API Requests to external server very slow to process - mirth

Question

In this question Mirth HTTP POST request with Parameters using Javascript I used a semblance of the first answer. Code seen below.
I'm running this code for a file that has nearly 46,000 rows. Which equates to about 46,000 requests hitting our external server. I'm noting that Mirth is making requests to our API endpoint about 1.6 times per second. This is unusually slow, and I would like some help to understand whether this is something related to Mirth, or related to the code above. Can repeated Imports in a for loop cause slow downs? Or is there a specific Mirth setting that limits the number of requests sent?
Version of Mirth is 3.12.0
Started the process at 2:27 PM and it's expected to be finished by almost 8:41 PM tonight, that's ridiculously slow.
//Skip the first header row
for (i = 1; i < msg['row'].length(); i++) {
col1 = msg['row'][i]['column1'].toString();
col2...
...
//Insert into results if the file and sample aren't already present
InsertIntoDatabase()
}
function InsertIntoDatabase() {
with(JavaImporter(
org.apache.commons.io.IOUtils,
org.apache.http.client.methods.HttpPost,
org.apache.http.client.entity.UrlEncodedFormEntity,
org.apache.http.impl.client.HttpClients,
org.apache.http.message.BasicNameValuePair,
com.google.common.io.Closer)) {
var closer = Closer.create();
try {
var httpclient = closer.register(HttpClients.createDefault());
var httpPost = new HttpPost('http://<server_name>/InsertNewCorrection');
var postParameters = [
new BasicNameValuePair("col1", col1),
new BasicNameValuePair(...
...
];
httpPost.setEntity(new UrlEncodedFormEntity(postParameters, "UTF-8"));
httpPost.setHeader('Content-Type', 'application/x-www-form-urlencoded')
var response = closer.register(httpclient.execute(httpPost));
var is = closer.register(response.entity.content);
result = IOUtils.toString(is, 'UTF-8');
} finally {
closer.close();
}
}
return result;
}