Nosto's product indexer uses Magento's built-in indexer logic. In practice, Nosto indexer saves a serialized Nosto product object into a database. When Magento indicates that product data has been changed Nosto indexer will save the product data into the Nosto index if product data significant to Nosto was changed. When the indexer is used, product API calls to Nosto are made only when Nosto product data has been changed.