How to create a cloud database?

This depends on several factors, such as how much data you plan to store in your database and how many queries will be made in a given time frame. Essentially, you'll want to have a Linode that is only used for your database, then you'll need to configure remote access to your database from your two other Linodes. If the Linodes will all be in the same data center, you can communicate over the private network so that your database transactions don't count against your total network transfer pool. With regards to which plan to choose, you may want to review our guide for choosing a Linode. If you provide some more detail about your configuration, the Linode Community here may be able to provide more specific advice too.