What to read on application architecture?

Question

Yii

I am engaged in a project where the API is used.
Now the structure is as follows:
1st layer: API client.
2 layer: management and authorization 1 layer.
3rd layer: models with available methods.
Then it became clear that more layers were needed:
4th layer: caching.
Layer 5: models over models: grouping methods into usable methods (adapter, I guess).
It turns out that part of the application will use layer 3, part 4, part 5. Several questions arise at once:
1. Is such a structure normal?
2. What if you want to use layer 5 but without caching?
3. How to properly store models (suppose layer 3 is /models/modelX, how should layer 5 models be called)?
4. What are the specialized books where examples of solving such issues are explained in a clear language?
Thank you.

Answer 1

Read DDD by Eric Evans and Corporate Patterns by Martin Fowler.
Switch from Yii to ZF2 or SF2 to write really complex stuff.

Answer 2

I join Evans DDD and unit testing.
I’ll add on my own - here’s another good article-book from macrosoft:
https://msdn.microsoft.com/en-us/library/ff650706.aspx

Answer 3

The fifth layer is perhaps called a service? Which is in MVCS.