This depends on the server - they dont all act the same.
But in any case generally you should avoid installing without updating first.
And Yes there is... well it doesnt update your DB .. but its sorts your mirrors which would require a DB refresh ...
(I find it heinous so its turned off .. up to you how you feel about it)
I guess I should note ..
pamac always refreshes the db before installing .. so if you only use that to install software this service running shouldnt nip you.
pacman doesnt do that. So You would have to run
-Syy every time. Though .. we dont do that without including the
u (for update) .. so it means if you have this service and use pacman you should always use
pacman -Syyu ... or turn the service off and manage your mirrors/use pacman as you normally would.