More than one way to do this. One way is using marketo smart campaigns to keep track of product scores and use a webhook to compare and evaluate the scores.
Create custom score fields for each product. Create a custom text field to save the highest scoring product
Create smart campaigns to increment scores based on product pages visited. If you organised your website by products (e.g. domain.com/productA/ ; domain.com/productB/ ; domain.com/productC/ ), this will be easy:
Write a handler to compare and evaluate the highest score product, create a webhook with each product score in the payload, save the response to the custom text field, create a smart campaign to call the webhook (you may want to limit the webhook calls to once per hour)
webhook example in php
<?php
$scores = [];
foreach($_POST as $key=>$value)
{
$scores[$key] = $value;
}
arsort($scores);
reset($scores);
if( $scores[key($scores)] == 0){
echo json_encode(['response'=>'']);
} else {
echo json_encode(['response'=>key($scores)]);
}
?>
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