Hi António,
The short answer if I got the question right is no, but I need to a bit of context on what you are trying to achieve to support you.
If by cloud you mean Outsystems PaaS, then this is not possible at all. Outsystems PaaS is a self-contained, highly automated and secure network restricted infrastructure, where such type of configuration is not supported.
If by cloud you mean a front-end server running on an IaaS provider connecting to another IaaS or Classic Infrastructure Database then the answer is: it's technically possible but highly unrecommended. Network latency and performance between this 2 components (Front-end and Database) are critical and adding any network delay between 2 providers is undesired and may lead to poor performance.
Hope this helps.