Coalesce on right hand table field with left join, or a better way?
no one has bothered with an answer  

an index on [HomePages] [Key]  

an index on [HomePageTranslations] [CultureName], [HomePageId]
and make it a unique constraint if appropriate   

the query itself looks fine to me 

you could probably just use a view and an index on [HomePageTranslations] [HomePageId] and have fine response
10s of thousands is not that much