Experienced developer/team in NiFi, MQTT, MQM-concept

This project involves development work with our device manager for our MQTT IoT devices.

You need to be experienced with using MQTT brokers and using MQTT/JSON protocol. Actually you need to be experienced with messaging concepts for MQM systems. You will need to be able implement request-reply messaging using only MQTT.

Before awarding you the project we will ask you question related to our project. So we will not just rely on description from previous work.

We are using NiFi to consume our MQTT data. So you or somebody in your team should have good experience with using NiFi and creating custom processors.

So our IoT Devices communicates via gateways to the MQTT Broker.
So there will be tasks like
– registering new Gateways and new Devices
– configuring new Gateways and new Devices
– receiving various messages (status, alarms and measurements) hat would lead to update the device database and possibly notifications
– monitor that devices are online

We also need to provide an API for client and an admin user interface
We already have NiFi set up and a database (PostgreSQL).

We now need somebody or a team implement the different features which mean to be able to receive device messages and also send commands to the devices (configuration or commands to read measurements or control a relay for example)

To summarize we need the following skills:

MQTT
JSON
Database Design
NiFi
Java
REST API

Possibly we will develop a admin user interface but that we can ourselves if needed.

Please describe how you understand the requirment and relate it to something that you have done.