Keychain issues after Sierra

I've updated to MacOS Sierra a few days ago, and it has been really unstable (a lot of freezes and hangs, specially in XCode).

I noticed that in Console, the following two lines appear repeatedly, for different apps and services:

switching to keychain-db: /Users/user/Library/Keychains/login.keychain-db from /Users/user/Library/Keychains/login.keychain (0 1 1 1)
not switching as we're not in ~/Library/Keychains/: /Library/Keychains/System.keychain (0)

Is there any issue with keychain? Could that be causing the freezes?

tldr: No, you don't have an issue going on with keychain. Yes this could be a contribution to the hanging and very slow systems right now.

I have also been experiencing SERIOUS freezes with everything. I also have these same log messages for nearly every currently running application/task being spammed into the console at a ridiculous rate. Running terminal commands takes 10+ seconds in between input and forget a git status with this.

Apple has always had an unreasonable fetching rate for AddressBook, Calendar, and other apps which always cause these log issues since el capitan.

Currently Safari and WebKit is being added into this mix with it being quite unstable and has been since Sierra's beta throwing these log errors.

<compose failure [shared UUID]>

The log rate is quite substantial and is more than likely the reason or atleast a major part in our very slow systems right now.

Mid 2012 Macbook Pro Retina 2.6GHz Intel quad core here and I've never had it this bad.

No, I don't think it could be causing the freezes, something else would be causing the freezes. You should only worry about that log in the console if you are having problems specifically with the mail app, contacts, or calendars app(related to syncing or retrieving data from server).