You may have noticed some slowness over the last days, but be reassured, everything will be back in order soon:
Some maintenance is performed on the database (new indexes, new collations and new tables).
Also, the HTTP daemon will be stopped for upgrades and tuning during the next hours.
Everything will be back in order when the poor server (it needs more RAM) will read and write several files.
You'll find out that some new word list have been installed (searched keywords and phrases).