Hi Shuvo, AWS Lambda works as follow: 1) When you invoke a lambda function the first time, AWS creates a container (cold start) 2) AWS executes your lambda inside the container 3) After the execution, AWS put the lambda in a pool for some time (about 15 min) to be resued 4) Next execution, AWS checks if there is any container available and uses that one (warm start) You pay only for the time the lambda executes, not for the time the Lambda container is put in the pool and kept warm