Amazon RDS - DB Instances

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A DB instance is an isolated database environment running in the cloud which can contain multiple user-created databases. It can be accessed using the same client tools and applications used to access a standalone database instance. But there is restriction on how many DB instances of what type you can have for a single customer account. The below diagram illustrates the different combinations based on the type of license you opt for.

Each DB instance is identified by a customer supplied name called DB instance identifier. It is unique for the customer for a given AWS region.

DB Instance Classes

Depending on the need of the processing power and memory requirement, there is a variety of instance classes offered by AWS for the RDS service.

Instance Class	Number of Vcpu	Memory Range in GB	Bandwidth Range in Mbps
Standard	1 to 64	1.7 to 256	450 to 10000
Memory Optimized	2 to 128	17.1 to 3904	500 to 14000
Burstable Performance	1 to 8	1 to 32	Low to Moderate

When there is a need of more processing power than memory requirement you can choose the standard instance class with a higher number of virtual CPUs. But in the case of very high memory requirement you can choose Memory optimized class with appropriate number of VCPUs. Choosing a correct class not only impacts the speed of the processing but also the cost of using service. The burstable performance class is needed when you have a minimal processing requirement and the data size in not in peta bytes.

DB Instance Status

The DB Instance status indicates the health of the DB. It’s value can be seen from the AWS console or using AWS CLI command describe-db-instances. The important status values of DB instances and their meaning is described below.

DB Instance Status	Meaning	Is the Instance Billed?
Creating	The instance is being created. The instance is inaccessible while it is being created.	No
Deleting	The instance is being deleted.	No
Failed	The instance has failed and Amazon RDS can't recover it.	No
Available	The instance is healthy and available.	Yes
Backing-up	The instance is currently being backed up.	Yes