Given appropriate amount of memory and CPUs, Dgraph is quite fast at writes. I would suggest you to try to write in a concurrent manner and check performance. If you get any exceptions due to concurrent transactions, simply retry them.
Please do open a new post with details if you see performance issues.
Thank you again, It got slower the more results I added to a search. When I started the next search it was fast again. I think the problem was the speed of the lookup to get the ruid as i added more and more results. I added an indexed field to the Result with the document id in and used a filter
srch as r(func: eq(querystring,"%s")){
uid
ruid as result@filter(eq(result.documentid, "%d"))
}