@ssivaranjani.enginee : The fact that this all seems like magic to you is a pat on the back for the Bolt development team.
While we do believe that "We stand tall on the shoulders of great men", we have spent quite a few years understanding the technology required to get these things done.
To put it simply, we have used hardware and Cloud service available to anyone who is looking, and written codes of our own to enable collection of the data, and communication of the same over the internet to the required outputs.
Explaining each and every system would take quite a bit of time, and effort.
Now a direct answer to your question is
1) The controller is an ESP8266 module. The ESP8266 module is developed by a company known as Espressif and contains several different hardware chips which are controllers by themselves. The module allows us to write codes which can do data collection and transmit the same to our Cloud. While the Bolt WiFi module hardware is essentially an ESP8266 module with required pinouts, and power supply circuits, what makes the hardware a Bolt WiFi module is the firmware (code that we wrote) running on it.
2) We used Cloud services from Amazon Web Services and Digital Ocean to create boxes /droplets online (Much like the once we had you create), and wrote codes to host the website, and collect the data sent by the BoltWiFi module. The MQTT broker is running on these boxes/droplets, so I can't comment on what hardware the MQTT broker is running on, you will have to ask AWS or DigitalOcean for the answer.
3) A separate code allows you to communicate with our Cloud services via API calls, and these API calls have been packaged in the form of python libraries and other libraries.
4) We require you to create the DigitalOcean droplet so that the code you run does not take processing resources of the Bolt Cloud. While the API calls do take the Bolt Cloud processing resources, the resources used by the API call are much much lower then if you had to run your Python code on the Bolt Cloud. We do this so that we can serve a much bigger customer base with the ease of development that we provide. Also, the threshold values are processed on your digital ocean droplet.
I hope this answer gave you at the least a general idea of the answers you were looking for.