Google Cloud Datastore

A really good video to begins with

https://developers.google.com/datastore/docs/concepts/overview

Reasons for not voting Datastore, for now

1. A new product, not an industrial standard yet
2. Maintenance and management
   GQL is read-only query, using API to update or remove kind, entity is a non-trivial task so far
3. Requires a learning-curve for RDB developers
4. Support and reliability
5. Provider and pricing, obviously Google only

Pricing

It's important to note that data stored in the datastore may incur significant overhead. This overhead depends on the number and types of associated properties, and includes space used by built-in and custom indexes. Each entity stored in the datastore requires the following metadata:

• The entity key, including the kind, the ID or key name, and the keys of the entity's ancestors.
• The name and value of each property. Since the datastore is schemaless, the name of each property must be stored with the property value for any given entity.
• Any built-in and custom index rows that refer to this entity. Each row contains the entity kind, any number of property values depending on the index definition, and the entity key.

See How Entities and Indexes are Stored for a complete breakdown of the metadata required to store entities and indexes at the Bigtable level and How Index Building Works for a detailed explanation of how datastore indexes are managed.

Resource	Free Default Daily Limit	Billing Enabled Default Limit
Stored Data (billable)	1 GB*	1 GB free; no maximum
Number of Indexes	200*	200
Write Operations	50,000	10 million per day**
Read Operations	50,000	10 million per day**
Small Operations	50,000	10 million per day**

^*Not a daily limit but a total limit.
^**The billing enabled limits are for Preview only. If you expect to exceed these limits while the service is in Preview please request a quota increase.