<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Event/etc/events.xsd">
    <event name="amoptimizer_process_ajax_page">
        <observer name="amoptimizer_image_replace_process" instance="Amasty\ImageOptimizer\Observer\AjaxImageReplaceProcessor" />
    </event>
</config>
