ruby on rails - Facebook put_wall_post results in sending crawler request to our url and this results in long wait -

i using ruby on rails , koala library interact facebook. use put_wall_post api post on user wall. api takes link , picture url among other parameters. before change on fb side few months back, picture url used show picture of our application (or whatever passed) when app posted on user's wall. fb later on changed mechanism , use link parameter.

when call put_wall_post api, fb gets call, use link attribute send crawler scrap page @ link picture og:image tag. after crawler call returns, put_wall_post api returns. simple wall post results in 2 round trips. noticed take 2-3 seconds or takes 8-9 seconds before crawler comes our app page. put_wall_post api takes 2-3 on in cases 8-9 seconds before returns. , creating huge experience issue users since whatever doing (which resulted in wall post) takes long , have wait... note can't call put_wall_post on background thread outcome of needs reflected user in way...

why fb have use mechanism opposed previous way of looking @ picture url? why have send crawler in synchronized manner? why can't return put_wall_post , send crawler in async manner?

has seen delay issue? solution this?