Improve IoT App Performance & Backend Transition

I already have an IoT mobile app with its backend up and running; however, the user experience suffers from noticeable latency. My goal is to polish the codebase, trim anything that consumes resources... (Budget: ₹4000 - ₹5000 INR, Jobs: Backend Development, JavaScript, Linux, Mobile App Development, MQTT, Node.js, Ubuntu, VPS)