Node Replay in Progress on steemdb - What does it mean?

Hi Steemians, I hope you all are having a great day and time?

There's something that's bugging me and I really want to understand what it means.

I normally use steemd.com to explore the Steemit blockchain and know what and what is happening on my profile.

But today, I've been trying to use the site but it is not working and is displaying an error message or a notification.

the message reads: Node replay in progress

I don't understand what this message means and I want to know what it means.
I also believe that in future if this kind of event happens again, someone else will also want to know what that message means.

So please can anybody educate me about what that message means?

Thank you.

Happy Steeming