# Using the Query API


The following sections briefly discuss the parameters and request authentication used with the Query API.

For general information about how the Query API works, see [Query requests](https://docs.aws.amazon.com/AWSEC2/latest/APIReference/Query-Requests.html) in the *Amazon EC2 API Reference.*

## Query parameters


HTTP Query-based requests are HTTP requests that use the HTTP verb GET or POST and a Query parameter named `Action`.

Each Query request must include some common parameters to handle authentication and selection of an action. 

Some operations take lists of parameters. These lists are specified using the `param.n` notation. Values of *n* are integers starting from 1. 

For information about Amazon RDS Regions and endpoints, go to [Amazon Relational Database Service (RDS)](https://docs.aws.amazon.com/general/latest/gr/rande.html#rds_region) in the Regions and Endpoints section of the *Amazon Web Services General Reference*.

## Query request authentication


You can only send Query requests over HTTPS, and you must include a signature in every Query request. You must use either AWS signature version 4 or signature version 2. For more information, see [ Signature Version 4 signing process](https://docs.aws.amazon.com/general/latest/gr/signature-version-4.html) and [ Signature version 2 signing process](https://docs.aws.amazon.com/general/latest/gr/signature-version-2.html).