run two app runner services frontend (react)public and backend (nodejs) private

Hi,

i am currently working on app runner services, we have two applications one is frontend with react and backend with nodejs which gona talk to RDS. i want to deploy frontend with public endpoint and backend with private endpoint, im able to deploy but how can i make public frontend react to communicate with backend nodejs which is in private endpoint. the backend is communicating with RDS it is ok but how can public react app can communicate with backend nodejs. im scratching my head could any buddy please help me out of this....
thank you