Farming is one of the primary resources to provide human food therefore, it takes a large amount of cultivated land to meet food needs. Currently, technologies such as IoT have significant role in advancing agriculture in this digitalize era by improving conventional agriculture methods by not only making it optimal but also making it cost efficient for farmer to produce quality of crops. The aims of this paper to develop system in the form of REST API service by using.net 6 as framework to efficiently manage the growth of IoT devices from the ground up in medium scale to large scale cultivated land with easy to scale up based on the SignalR library and crops health monitoring. The system will assist institute farmer and technician by visualizing data from each deployed IoT device (Temperature, humidity, soil moisture, Ph) from each section of cultivated land and management of each new IoT device such as sensor, actuator and microcontroller that will be deployed and by using SignalR library as an interconnection between device to API. To ensure the quality of the system author measured using the JMeter application by conducting simulation with high peak of user access and transmitted data of IoT device to give a validation of load testing that the system will run smoothly without any problem. The research concludes based on the testing that been done has successfully delivered and shown no latency or error with performance result on each test 21ms functional and 0.50ms on SignalR testing.