Design a large-scale temperature sensor system

## System design: large-scale temperature sensor collection and visualization Design a system to **collect and display temperature data** from a very large number of sensors distributed across a wide geographic area (e.g., Washington State). ### Inputs / devices - **1 million to 10 million** temperature sensors, roughly uniformly distributed. - Sensors are **low-cost and simple**. - Sensors **do not support mesh networking**. - Sensors send readings to the backend via **HTTP** (both sides have IP addresses). - Temperature changes slowly, but the system must be able to **track any sensor’s temperature over time at 10-second granularity**. ### Outputs / product requirements - A **near real-time temperature distribution map** for a Web UI. - At ~1M sensors, the UI can show roughly **1 sensor per pixel** on a 4K display. - Support queries over a time range (e.g., **1 day** or **1 year**) to retrieve: - **current temperature** - **minimum temperature** - **maximum temperature** - The system should run **reliably for years**. ### What to cover - High-level architecture, APIs, storage, and data flow. - Scalability, reliability, and operational concerns. - How you serve both near-real-time visualization and long-range historical queries.