Our plugins simply import products from social networks or other websites to WordPress/Woocommerce. This means that AFTER the import, WordPress/Woocommerce handles the rest of the process (frontend/backend products listings). The fact that the website is slowing down is because of WordPress Database Architecture. The WordPress platform was not intended for large shop-like databases, so if you`re trying to import a gazzillion number of Amazon Products, each one with all its variations you need to have MORE RESOURCES (MORE RAM, MORE CPU). Of course, at one point WordPress will eventually crash because of the large amount of data that needs to be processed by it. You can increase this limit by getting a better hosting provider.