How i can share information from my MicroService A's postgers DB to MicroService B - postgresql

Question

I have created Four micro services. First service only handles registration n login module(A), Seconds service has the Post& Comment Module(B),Third services has Rating & Review Module (C)and ADMIN Module (D).
Problem
All micro services has their own database.But Service B is dependent to service A's DB. Service C is dependent to B and A's DB and Service D is also dependent to service A,B,C. I'm using postgres DB for all service A,B,C .
Option 1.
I can use JDBC connection Factory and connect service B to service A DB.But this is not a good practice b'coz if Service A changed their column then we have to change Service B module.
Option 2.
I can create Hot-standby replica of my service A and Service B but the problem here Hot-standby replica is Read Only i can't perform update n delete.

Answer 1

You should design your microservices so they don't need any dependency on other microservices. Otherwise it looks like distributed monolith. No matter if dependency is established on microservice level or any kind of database linking as both your options suggest.
IMHO the clean solution is:
think over again if you really need such granularity
if yes, then for each database, declare all entities needed by particular microservice. Duplicities are not problem - if B module (posts) needs database of users, let it have it's own copy of users table, not link to A module.
connect microservices by reliable messaging system (Kafka) in which an event in one microservice propagates to listeners in other microservices and let them update their data models
There is a lot of redundancy in this model, however it's robust and definitely closer to really distributed system. We successfully use it in our big fintech platform.