During the issue we were able to observe unusual and constant traffic on the VM that hosts the affected services. After conducting several security checks, we were able to rule out that it was due to a DDoS attack.
The cause of the increased response time could be due to the constant lack of RAM, however, it must be taken into account that no routine maintenance was performed on this VM for at least 200 days.
As RAM was lacking, pending operations were left in a kind of queue, collapsing future operations and requests.
We will work hard so that it doesn't happen again.