Redis - Redis is an open source in-memory data structure project implementing a distributed, in-memory key-value database with optional durability.
Firebase - Firebase is a cloud service designed to power real-time, collaborative applications for mobile and web.
SQLite - SQLite Home Page
Supabase - An open source Firebase alternative
PouchDB - Open-source JavaScript database inspired by Apache CouchDB that's designed to run well within the browser
neo4j - Meet Neo4j: The graph database platform powering today's mission-critical enterprise applications, including artificial intelligence, fraud detection and recommendations.