と同時に

The expression と同時に can be used to express that an event takes place at the same time as another event, or that two separate situations are both simultaneously the case. It can be translated as "as soon as", "at the same time", "as well", or "also."

電車のドアが開くと同時に、多くの人が降りて来た。
The moment the train's doors opened, a bunch of people got off.

新しいゲームソフトは発売されると同時に、全部売れてしまった。
As soon as the new game was put on sale, it sold out completely.

12月に入ると同時に、急に寒くなった。
It quickly became cold as soon as we entered December.

この絵本は読んで面白いと同時に、考えさせられる。
I read this picture book and it was interesting, and it also made me think.