My colleague was working on migrating around dozens of batch jobs written in Java. All jobs had JPA/Hibernate but people which were writing those jobs didn’t understand abstraction and encapsulation. It end-up as vendor locked as you can imagine. Procedures, reading cursors, Oracle specific functions, metadata, logic spread between Java and PL/Sql, all the fun stuff, you know. So it took around one year of work to migrate to Postgres. And that’s with support of DBA who was helping with rewriting most complicated queries and procs. So yeah, don’t worry about that DBMS specific features.

Don’t get me wrong, though. Efforts spent on making design decisions should be proportional to potential size/complexity growth of the software. If you building todo list , how many different queries you might have in fairly pessimistic scenarios? Maybe couple dozens. Don’t bother with JPQL or HQL. If you expect your app to grow significantly. I’d do as much as possible to avoid my colleague’s fate.

Please, can you give an example of such code snippets? I’m wondering what people consider reusable in different projects.

To me, generated code should not be committed at all. Again, I know nothing about this stack but code generators can have different behavior on different machines due to versions, flags and even OS. To deliver consistent results they should run in consistent env. It’s build time concern which CI/CD should take care of.

I didn’t get do you do integrations besides of your DB.

To me architecture sounds good anyway. I’m not GO dev but it looks like stack is your main problem not architecture itself. Multiple models is great long term approach which makes sure you are not leaking implementation details of your persistence/3rd party services to your client. You have layer of mappers where you can enrich model in optimal way and at the same time you can accommodate whatever client request/payload quirks you may need. Yes it’s sometimes annoying to add one field and pass it across all layers but it’s the price and software development is all about balance and compromises. I worked in projects that didn’t follow this architecture and any kind of change in DB/3rd party were cascading through entire application so end up changing hundreds of files instead of couple of models and few mappers

You may have issues with this architecture if you invoke services directly one from another for complex use cases. This can couple things together. If that’s what’s happening think if can apply Facade. Try using/reusing more trivial and focused services in Facade to make sure that for example Order service does not depend on Client service. Leave it to ClientOrderFacade.

First of all, what you are doing is integration via DB. Unless that was conscious, I would avoid using this approach. System is much easier to manage when DB/schema used at most by one app. You have two ways to achieve it, move towards micro-services or monolith. Yes monolith is still great for some use cases.

If we talking about your current system state every app should do changes in most backward compatible way. It worst cases it will lead to duplications. Let’s say if you want to change table X because there is such need for app A and at the same time app B uses this table. Instead of modifying X you create table Y that satisfies needs of A and make sure that data written into Y as well as into X to maintain B.