Technically speaking, what's a good way to connect to data sources for cloud apps? I'd be nervous to let cloud apps [or hackers thereof] to slurp arbitrary bits

Technically speaking, what's a good way to connect to data sources for cloud apps? I'd be nervous to let cloud apps [or hackers thereof] to slurp arbitrary bits of data through JDBC. Quite a bit more comfortable having the connection happening from on-prem workstations.