If you create any Destination in the Audience Manageer UI, or map segment to a destination, then it will take 2 to 3 hours to be effective. Then after that, segment sharing with destination will be at real time. For example URL and Cookie destinations fire at real time. If the visitor qualifies for a segment, and if that segment is mapped to a cookie or a URL destination, then cookie will be written in browser or URL destination pixel will fire.
For Server to Server Destinations:
Once a batch S2S destination has been created by your consultant or Adobe Customer Care team, then it will take upto 48 hours to send the first batch file (Full Sync). Then after that an iterative sync batch file will be sent every 24 hours for the new synced IDs.
In case of Real time S2S destination, it takes 2-3 hours after it has been created by your consultant or Customer Care. Then, if AAM is implemented on your webpage or app, then AAM starts sending data (server to server) for segment qualification to Destination at real time.