Going from using only JPA/Hibernate for everything, to use a combination of both jOOQ and JPA/Hibernate on a project, is probably the best decision I've made. Using each tool at what I believe they do best.
I use JPA/Hibernate for most writing and inserts. It helps a lot when you're dealing with aggregates with child and child entities. It would be a nightmare to track all changes myself and try do manually do what the ORM is doing for me. Deleted a child of a child of an aggregate? No problem, persist only that.
I've started to separate my JPA/Hibernate entities from my domain models as well, and it looks promising. There's some more mappins, but my domain won't be polluted with database concerns.
Then I use jOOQ for almost all reading of data, reading into custom read models that fit the view they are supposed to be shown in. No problem doing multiple joins or other stuff that would give you an immediate headache when trying to solve using JPA/Hibernate.
How do you solve storing/updating/removing child entities of another entity (which also may be a child of another entity) effectively?
I use jOOQ as well, but mostly only for the reading part. For the above case, I still use Hibernate, as I've yet to find an efficient way to do it in jOOQ.
> I expect every single one of my backend engineers (on any tech stack) to understand the fundamentals of SQL INSERT, UPDATE, and DELETE statements.
Understanding INSERT, UPDATE, and DELETE doesn't help you very much when you have to persist changes to a single child entity of many in an aggregate (parent entity). How do you track which child has changed? Or if a new child is added? Or one is deleted? Or what if the relation is a child of a child of the aggregate, which might very well be the best way to model your domain.
In these situations, Hibernate/JPA will help you a lot! If you're doing it using plain SQL/JDBC, you'll probably end up writing your own mini ORM, and/or polluting your domain with database concerns. (I do keep my Hibernate entities separated from my domain.)
Complex queries with multiple joins? jOOQ.
Persist changes to complex aggregate models with multiple layers of child entities? JPA/Hibernate.