> Because that single application already exists, in my case its postgres.
This is exactly what postgres was designed for! Tens of thousands of hours of work over decades to solve the problem of relational database management. That's why we call it an RDBMS!
Which isn't to say you shouldn't make your own API ever. There are a lot of situations where you don't want things to connect directly to postgres.
But you shouldn't be afraid of having multiple systems connect to postgres. It has incredibly mature and robust features to accommodate that use case. It's the expected use case.
This is exactly what postgres was designed for! Tens of thousands of hours of work over decades to solve the problem of relational database management. That's why we call it an RDBMS!
Which isn't to say you shouldn't make your own API ever. There are a lot of situations where you don't want things to connect directly to postgres.
But you shouldn't be afraid of having multiple systems connect to postgres. It has incredibly mature and robust features to accommodate that use case. It's the expected use case.