With Ruby on Rails 5+Puma+Nginx configuration, is it a specification that the memory is released at a fixed time?

As the title suggests, is it a specification that Rails 5+Puma+Nginx configuration releases memory at a fixed time (around 57 minutes per hour)?

The main versions used are as follows:

• Ruby: 2.4.2
• Ruby on Rails: 5.0.6
• Puma:3.11.2
• Nginx:1.12.2

There are three servers and they are configured as follows:

A server (Nginx) BB server (Puma)
                  └ C Server (PUma)

I thought it was probably Puma's memory, so I checked if Puma has such a function, but I couldn't check the specifications.(When memory is released, Puma's worker process ID changed, so Puma's worker seems to have restarted.)

Below is a graph of Memory Used% in NewRelic, where the blue and red lines are running Puma, and you can see that memory usage drops sharply around 57 minutes per hour as described above.

By the way, I don't use puma_worker_killer.

So I asked you, is this the specification of Puma, Nginx (or Rails)?If this is the specification, please let me know if there is a document with the specification.