When data sent to the server is written from memory to storage

I'm studying computer configuration and design.

The computer has primary and auxiliary memory, each of which consists of SRAM&DRAM, and magnetic disks. Because the main memory is an electrical system, it can be accessed at high speed, but data cannot be held when it is shut down.
Although auxiliary storage is low speed because it is a mechanical system, data can be written to a magnetic disk and stored.
Do you understand that

For servers that multiple users can use remotely for data management,
When the user sends the data, the application running on the server receives
How is it stored in the database?

Is there a case where it is first stored in the main memory and then stored in the auxiliary memory after checking the timing?