MySQL - The world's most popular open source database
ThingSpeak - Open source data platform for the Internet of Things. ThingSpeak Features
PostgreSQL - PostgreSQL is a powerful, open source object-relational database system.
AWS IoT - Easily and securely connect devices to the cloud.
SQLite - SQLite Home Page
Azure IoT Hub - Manage billions of IoT devices with Azure IoT Hub, a cloud platform that lets you easily connect, monitor, provision, and configure IoT devices.