Why are some syncs taking a really long time, especially historical syncs?
Connector: Apple App Store
If there is a lot of data, it is recommended that data for only one app is synced per connector.
The cause of this is due to limitations in the number of requests available per minute from the Apple API. More information about this issue can be read in their API documentation.
Apple applies an aggressive API request limit which can be as low as 4 requests per minute. If a sync has to sleep for 60 seconds every time it makes 4 requests, this adds significantly to the delays.