TLS encryption is used on the MQTT protocol, but no other specific security features are used. A custom certificate handling system has been built for short-lived and device-specific IoT device certificates, so a custom security model has been built. AWS IoT Core is used for the core only, and events are streamed to Kafka where they are further processed. Whether AWS IoT Core or another solution is used, it would not make that big of a difference because it just throws the events to the Kafka broker. There are no lacking features because the pure core is used and the rest is managed in-house. Discussions have been had with the AWS team itself. If AWS IoT Core is used just for basic functionality, it is very expensive. Price calculations were done together with AWS, the core product team, and the product manager for AWS IoT Core. They made an adaptation, and a few quarters ago, they introduced a feature that allows paying a decent price for just using the basic things that are needed. The price setting point of view is satisfactory. Building it ourselves was looked at because it was too expensive. Some open source tooling was considered because the key thing about having a good solution is that the open source tools that could be found were more than enough. The key thing is, of course, to make it resilient.
