Is there any limitation of data sync through APPSeCONNECT?

There is no limitation in terms of data sync through APPSeCONNECT. Thousands or millions of data syncs which do not affect APPSeCONNECT cloud account since it is not storing any data in between. The data sync will directly happen between your own servers. Performance of the sync processes depends on the platform, version and tools used in data sync. For example, SAP Business One DI server provides quicker data sync than SAP Business One DI API. Open source eCommerce platform APIs might work more faster in data sync than hosted eCommerce’s APIs.