An Application hosted in the Cloud (PaaS or IaaS) needs access to data originating from an on-premises database. This includes establishing connection to an on-premises database or a cloud database replicate of the on-premises database.
Example include:
- Lift and shift of custom developed application and data resides on premises
- A Business Intelligence Cloud Service needs access to a copy of data that resides on premises
Patterns applicable for this use case can be found here
Hybrid and Multi Cloud 