Which service is used for building IoT applications in AWS?

Amazon IoT Core is specifically designed for building Internet of Things (IoT) applications on AWS. It enables you to connect devices securely to the cloud and interact with other AWS services. This service allows you to easily manage and communicate with a large number of devices and provides features such as device authentication and secure communication protocols, which are essential for the functionality of IoT applications.

With Amazon IoT Core, you can ingest data from devices, process that data, and integrate it with other services like AWS Lambda or Amazon S3, which can be valuable in creating complex IoT solutions. This capability makes it the primary service tailored for building and scaling IoT applications within the AWS ecosystem.

Other services like Amazon S3, while useful for data storage, do not offer the unique functionalities necessary for handling IoT devices. Amazon EC2 provides computing resources but lacks the connectivity and management features required specifically for IoT. Amazon Lambda can be part of an IoT solution for running code in response to events but does not serve the overarching needs of connecting and managing IoT devices on its own. Thus, Amazon IoT Core stands out as the dedicated service for IoT application development in AWS.