Services
Data Storage
Just because you've gone JAMstack doesn't mean you can't get data from a database or otherwise store and retrieve data.
8base
Data storage, GraphQL access to that data, and easy Lambda deployment.
Airtable
Part spreadsheet, part database, and entirely flexible.

AWS AppSync
Fully managed database agnostic GraphQL API service with first-class support for real-time and offline.
Check out projects like Conference App in a Box which use AppSync to make comments real-time.

FaunaDB
FaunaDB is priced based on your usage, and offers a free tier.

Firebase Cloud Firestore
Cloud Firestore is a flexible, scalable database for mobile, web, and server development from Firebase and Google Cloud Platform.
Firestore is newer and Google encourages you more to use it over Firebase’s original realtime database. Comparison .
Firebase Realtime Database
Perhaps Firebase Realtime Database’s most useful and iconic feature is the realtime data storage feature. Once you connect, you can not only push data to the realtime database, but watch and respond to data changes in near realtime.

Hasura
Hasura is an open source engine that connects to your databases & microservices and auto-generates a production-ready GraphQL backend.
Hoodie
A fast, simple and self-hosted backend as a service for your (web) apps, Open Source and free. No need to write server-side code or database schemas. Makes building offline-capable software a breeze.
JSONbin.io
JSONbin.io is a free JSON storage and JSON hosting service. It is an ideal solution for storing JSON data for small-scale web apps, mobile apps, or websites.
There is also JSONbin.org , which is very similar.
MongoDB
MongoDB Atlas is the cloud database. MongoDB Realm is the serverless platform.

n:point
JSON storage bins that won’t break your app. Set up a lightweight JSON endpoint in seconds, then add a schema to edit your data safely at any time.
Para
Para is a flexible and cost-effective backend service that stores, indexes and caches your objects.
Realm Database
An open source alternative to SQLite and Core Data.

Sheetsu
Sheetsu helps you connect Google Sheets to anything - Web, Mobile, IoT or any service’s API.
Google Sheets has an API directly , but it’s not particularly easy to use. Sheetsu makes it less sheety. Get it. That’s not their tagline I just wrote that. Also look at Tabletop.js for an open source library to help with the Google Docs API.Supabase Database
Open Source SQL Database – without the hassle. The Open Source Firebase Alternative.
Create a backend in less than 2 minutes. Start your project with a Postgres Database, Authentication, instant APIs, Realtime subscriptions and Storage.
Every Supabase project is a dedicated PostgreSQL database. PostgreSQL is one of the worlds most scalable databases.