A 1.7 world was created for a Fresh server, with 5GB of RAM and a player slot availability of 100 (set by the host).
After a fresh server start the server seems to hold up fine for the first 30 minutes but after 5-7 players start logging in or out, or are playing for a little while the server starts suffering from severe lag.
We'll notice that breaking blocks and using chests is very delayed and laggy. Any attempts to ride horses is an utter failure from being stopped for a few minutes to wait for the server to catch up again.
Information I think that is beyond our control, Will probably need a fix from Mojang:
https://mojang.atlassian.net/browse/MC-39037
This is all of course without plugins as CraftBukkit is not updated yet.