Embever has developed an energy efficient cloud-to-device-communication service for low-power IoT devices. “Embever Core” is a cloud-based middleware designed for developers to connect battery-powered IoT devices with their web applications in an easy and energy-efficient way. Embever provides firmware and hardware components for the devices that use optimized protocols to communicate with the Embever Core. The Embever Firmware enables devices to fall into deep sleep mode and to synchronize with the middleware depending on flexible settings. The intelligent messaging cache system of Embever Core ensures that no data gets lost while the devices are in deep sleep mode.