So if Customer A connecting app from market place, after provide the grant access, the applicaton will redirect to https://example.com/hubspot/integrate ?
and If Cusotmer B connecting app from market place, after providing the grant access , then the application will redirect to the same url which is https://example.com/hubspot/integrate ?
Spot on! The redirect uri is the url that visitor gets redirected to after granting access to your integration app. In the scenario that you detailed down, both Customer A and B will be redirected to the same url which is the redirect uri. This redirect uri is also used in this endpoint Get OAuth 2.0 Access Token and Refresh Tokens and it must exactly match the redirect uri used here -initiating the OAuth 2.0 connection.