Get an introduction to the concept of consumer-driven API contracts, and how to implement this with Pact, Spring Boot, and an API consumer and provider.
If you're looking to test your IoT app's communication, here's how JMeter can load test the popular MQTT protocol, with an overview of the protocol itself.
Throughout application development, you need to make CRUD operations on our stored data. Postgres and the Time API can help you map JPA in your database.