This is the 13285th most frequent Korean word.
들어오자마자
"As soon as (someone) enters."
The phrase '들어오자마자' is used to indicate an action that happens immediately after entering a place.
그는 집에 들어오자마자 양말을 벗었다.
As soon as he entered the house, he took off his socks.
Here, '들어오자마자' highlights the immediacy of noticing something upon entry.
들어오자마자 불이 꺼진 것을 발견했다.
As soon as I entered, I noticed that the lights had gone out.
In this context, '들어오자마자' emphasizes the prompt reaction of the shop owner upon someone entering.