Later today or maybe tomorrow I will upgrade the database server to the latest stable version of MariaDB. During the upgrade the page(s) won't be reachable. Expected downtime: 30 minutes.
Network timeline is loading horribly slow. There are two queries to load the content - first query is for the posts, second query is for the related comments and reactions, I guess. The first one is running for 30 seconds, the second one for 3-5 minutes!
I have changed the setting for query optimizer to use a more simplistic method. Now the network page seems to be much faster again.
Step 1: Set nodes into maintenance mode
Step 2: Stop the MariaDB service
Step 3: Install the update
Step 4: Restart everything
Downtime 30-60 minutes.