free tier gives 512 MB

Managed Memcache service. Free for up to 25MB, 1 Proxy Server, and basic analytics

a fast and straightforward NoSQL cloud database service. With restdb.io you get schema, relations, automatic REST API (with MongoDB-like queries), and an efficient multi-user admin UI for working with data. The free plan allows 3 users, 2500 records, and 1 API request per second

Serverless Redis with free tier up to 10,000 requests per day, 256MB max database size, and 20 concurrent connections

Abstract ORM with a universal schema language for any database

Hosted managed MySQL database, CI integration & auto scaling

Timeseries database, free up to 3MB/5 minutes writes, 30MB/5 minutes reads and 10,000 cardinalities series

Cloud Native Cassandra as a Service with 80GB free tier

API-oritented Airtable alternative

Free CockroachDB up to 5GB and 1vCPU (limited request units)

Primarily a PaaS but offers a 128MB to 192MB free tier of MySQL, PostgreSQL, or MongoDB

Cloud Data Platform offers a free tier and all plans are completely free while in beta