Overview

Before connecting to a DB instance, you must create one first. For details about how to create a DB instance, see Buying an RDS for PostgreSQL DB Instance. You can connect to an RDS for PostgreSQL instance through a command-line interface (CLI), graphical user interface (GUI), Data Admin Service (DAS), or using Java database connectivity (JDBC).

Connecting to a DB Instance over a Private or Public Network Using CLI

Table 1 lists how to use CLI to connect to an RDS for PostgreSQL instance over a private or public network.

**Table 1** Connecting to a DB instance over a private or public network
Connection Method	IP Address	Security Group Rules	Description
Private network	Private IP address	If the ECS and RDS DB instance are in the same security group, they can communicate with each other over a private network by default. No security group rules need to be configured. If they are in different security groups, configure security group rules for them, separately. RDS DB instance: Configure an inbound rule for the security group with which the RDS DB instance is associated. For details, see Configuring a Security Group Rule. ECS: The default security group rule allows all outgoing data packets. In this case, you do not need to configure a security group rule for the ECS. If not all outbound traffic is allowed in the security group, you need to configure an outbound rule for the ECS.	Secure and high-performance Recommended
Public network	You need to purchase an EIP. For pricing details, see EIP Billing.	To access a DB instance from resources outside the security group that the DB instance is associated with, you need to configure an inbound rule for the security group. For details, see Configuring a Security Group Rule.	Less secure To achieve a higher transmission rate and security level, you are advised to migrate your applications to an ECS that is in the same VPC as your RDS DB instance and use a private IP address to access the DB instance.

Figure 1 Connecting to a DB instance over a private or public network

Connection Methods

**Table 2** Connection methods
Connection Method	Description
Connecting to an RDS for PostgreSQL Instance Through DAS (Recommended)	DAS enables you to manage databases on a web-based console and provides you with database development, O&M, and intelligent diagnosis to make it easy to use and maintain your databases. The permissions required for connecting to DB instances through DAS are enabled by default.
Connecting to an RDS for PostgreSQL Instance Through the psql CLI Client	In Linux, you need to install a PostgreSQL client on the ECS and connect to the instance through the psql CLI over a private or public network. A floating IP address is provided by default. When your applications are deployed on an ECS that is in the same region and VPC as the RDS for PostgreSQL instance, you are advised to use a floating IP address to connect to the instance through the ECS. If you cannot access your RDS for PostgreSQL instance through a floating IP address, bind an EIP to the instance and connect to the instance through the EIP.
Connecting to an RDS for PostgreSQL Instance Through the GUI	In Windows, you can use the pgAdmin client to connect to an RDS for PostgreSQL instance.
Connecting to an RDS for PostgreSQL Instance Through JDBC	RDS for PostgreSQL is compatible with the community ecosystem and does not provide the driver service. You can select a community driver version as required. If you are connecting to an instance through JDBC, the SSL certificate is optional. For security reasons, you are advised to download the SSL certificate to encrypt the connection.