In the event-based Salesforce to QuickBooks integration process, the data sync occurs in real-time. The process to integrate data gets invoked on the occurrence of an event (like new customer addition, new order placement, product information change in Salesforce or in QuickBooks). The other method is to schedule a cron job on the server or to create a scheduler in Salesforce that starts a batch process to sync data in the background with QuickBooks. You may choose to sync customers, products, orders, quotes (estimates), opportunities, invoices, notes, and attachments between Salesforce and QuickBooks.
QB Desktop Integration is done with the help of QuickBooks Web Connector or QODBC driver to interact with QuickBooks to access or store data in QuickBooks. Both the methods have pros and cons so we will suggest a better way according to your needs. For QB online QuickBooks REST api is used. On the other side, Salesforce SOAP/REST api can be used to access and store data in Salesforce CRM. For data sync from Salesforce to QuickBooks Salesforce triggers, batch apex code, scheduler features will be used and server-side web services will be created. Intermediate web services (that will act as middle-ware between Salesforce and QuickBooks) can be developed in any programming language of your preference (like NodeJS, PHP, Java or .NET code).