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Amazon Relational Database Service
User Guide (API Version 2014-10-31)

Managing Amazon Aurora PostgreSQL

The following sections discuss managing performance and scaling for an Amazon Aurora PostgreSQL DB cluster.

Managing Performance and Scaling for Amazon Aurora PostgreSQL

Scaling Aurora PostgreSQL DB Instances

You can scale Aurora PostgreSQL DB instances in two ways, instance scaling and read scaling. For more information about read scaling, see Read Scaling.

You can scale your Aurora PostgreSQL DB cluster by modifying the DB instance class for each DB instance in the DB cluster. Aurora PostgreSQL supports several DB instance classes optimized for Aurora. The following table describes the specifications of the DB instance classes supported by Aurora PostgreSQL.

Instance Class vCPU Memory (GiB)
db.r4.large 2 15.25
db.r4.xlarge 4 30.5
db.r4.2xlarge 8 61
db.r4.4xlarge 16 122
db.r4.8xlarge 32 244
db.r4.16xlarge 64 488

Maximum Connections to an Aurora PostgreSQL DB Instance

The maximum number of connections allowed to an Aurora PostgreSQL DB instance is determined by the max_connections parameter in the instance-level parameter group for the DB instance. By default, this value is set to the following equation (the log function represents log base 2):

LEAST({DBInstanceClassMemory/9531392},2500).

Setting the max_connections parameter to this equation makes sure that the number of allowed connection scales well with the size of the instance. For example, suppose your DB instance class is db.r4.large, which has 15.25 gibibytes (GiB) of memory. Then the maximum connections allowed is 1660, as shown in the following equation:

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LEAST( (15.25 * 1000000000) / 9531392 ), 2500) = 1660

The following table lists the resulting default value of max_connections for each DB instance class available to Aurora PostgreSQL. You can increase the maximum number of connections to your Aurora PostgreSQL DB instance by scaling the instance up to a DB instance class with more memory, or by setting a larger value for the max_connections parameter, up to 262,143.

Instance Class max_connections Default Value
db.r4.large 1660
db.r4.xlarge 2500
db.r4.2xlarge 2500
db.r4.4xlarge 2500
db.r4.8xlarge 2500
db.r4.16xlarge 2500

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