for example for keyword "backyard compost bin" if .com already taken so i choose backyardcompostbins.com and for keyword "hot kiss" hotkiss.com was taken, so i choose hotkisses.com does these make big sense to search engine, i know exact keyword is very very powerful for rank with less backlink
I sometimes use the plural in my domains. It works just fine. There is a lot more to SEO than the domain though, so don't fret too much about it.
Exact keyword domains only matter for low competion keywords. And for those, the plurar will do just fine --with proper backlinks. Pierre.
You wouldn't get the exact URL benefit from the search engines, which i believe has been given less priority after Google's June Algorithmic update. However, you will still get the benefit of having the targeted keywords in your URL which however is very insignificant as compared to the exact URL bonus. So you'll have to do more SEO than someone who owns the exact match domain.