Koster was previously the rabbi of the Village Temple, also known as Congregation B'nai Israel, in New York City, before joining the Village Temple, she was Associate Rabbi at Temple B'nai Abraham in Livingston, New Jersey.[2] In 2010 she was featured in the documentary Kol Ishah: The Rabbi is a Woman, directed by Hannah Heer.[2] In 2010 she was chosen to be the first female rabbi in Sweden; however she withdrew her name for "personal reasons."[3][4]