# Retrieving configuration data without AWS AppConfig Agent
The recommended way to retrieve configuration data from AWS AppConfig is by using the Amazon-developed and managed AWS AppConfig Agent. With the agent, you can cache configuration data locally and asynchronously poll the AWS AppConfig data plane service for updates. This caching/polling process ensures that your configuration data is always available for your application while minimizing latency and cost. If you prefer not to use the agent, you can call public APIs directly from the AWS AppConfig data plane service.
The data plane service uses two API actions, [StartConfigurationSession](https://docs.aws.amazon.com/appconfig/2019-10-09/APIReference/API_appconfigdata_StartConfigurationSession.html) and [GetLatestConfiguration](https://docs.aws.amazon.com/appconfig/2019-10-09/APIReference/API_appconfigdata_GetLatestConfiguration.html). The data plane service also uses [separate endpoints](https://docs.aws.amazon.com/general/latest/gr/appconfig.html#appconfigdata_data_plane) from the AWS AppConfig control plane.
**Note**
The data plane service replaces the previous process of retrieving configuration data by using the `GetConfiguration` API action. The `GetConfiguration` API is deprecated.
**How it works**
Here's how the process of directly calling AWS AppConfig APIs using the data plane service works.
Your application retrieves configuration data by first establishing a configuration session using the [StartConfigurationSession](https://docs.aws.amazon.com/appconfig/2019-10-09/APIReference/API_appconfigdata_StartConfigurationSession.html) API operation. Your session's client then makes periodic calls to [GetLatestConfiguration](https://docs.aws.amazon.com/appconfig/2019-10-09/APIReference/API_appconfigdata_GetLatestConfiguration.html) to check for and retrieve the latest data available.
When calling `StartConfigurationSession`, your code sends the following information:
+ Identifiers (ID or name) of an AWS AppConfig application, environment, and configuration profile that the session tracks.
+ (Optional) The minimum amount of time the session's client must wait between calls to `GetLatestConfiguration`.
In response, AWS AppConfig provides an `InitialConfigurationToken` to be given to the session's client and used the first time it calls `GetLatestConfiguration` for that session.
**Important**
This token should only be used once in your first call to `GetLatestConfiguration`. You *must* use the new token in the `GetLatestConfiguration` response (`NextPollConfigurationToken`) in each subsequent call to `GetLatestConfiguration`. To support long poll use cases, the tokens are valid for up to 24 hours. If a `GetLatestConfiguration` call uses an expired token, the system returns `BadRequestException`.
When calling `GetLatestConfiguration`, your client code sends the most recent `ConfigurationToken` value it has and receives in response:
+ `NextPollConfigurationToken`: the `ConfigurationToken` value to use on the next call to `GetLatestConfiguration`.
+ `NextPollIntervalInSeconds`: the duration the client should wait before making its next call to `GetLatestConfiguration`.
+ The configuration: the latest data intended for the session. This may be empty if the client already has the latest version of the configuration.
**Important**
Note the following important information.
The [StartConfigurationSession](https://docs.aws.amazon.com/appconfig/2019-10-09/APIReference/API_appconfigdata_StartConfigurationSession.html) API should only be called once per application, environment, configuration profile, and client to establish a session with the service. This is typically done in the startup of your application or immediately prior to the first retrieval of a configuration.
If your configuration is deployed using a `KmsKeyIdentifier`, your request to receive the configuration must include permission to call `kms:Decrypt`. For more information, see [Decrypt](https://docs.aws.amazon.com/kms/latest/APIReference/API_Decrypt.html) in the *AWS Key Management Service API Reference*.
The API operation previously used to retrieve configuration data, `GetConfiguration`, is deprecated. The `GetConfiguration` API operation does not support encrypted configurations.
## (Example) Retrieving a configuration by calling AWS AppConfig APIs
The following AWS CLI example demonstrates how to retrieve configuration data by using the AWS AppConfig Data `StartConfigurationSession` and `GetLatestConfiguration` API operations. The first command starts a configuration session. This call includes the IDs (or names) of the AWS AppConfig application, the environment, and the configuration profile. The API returns an `InitialConfigurationToken` used to fetch your configuration data.
```
aws appconfigdata start-configuration-session \
--application-identifier application_name_or_ID \
--environment-identifier environment_name_or_ID \
--configuration-profile-identifier configuration_profile_name_or_ID
```
The system responds with information in the following format.
```
{
"InitialConfigurationToken": initial configuration token
}
```
After starting a session, use [InitialConfigurationToken](https://docs.aws.amazon.com/appconfig/2019-10-09/APIReference/API_appconfigdata_StartConfigurationSession.html#API_appconfigdata_StartConfigurationSession_ResponseSyntax) to call [GetLatestConfiguration](https://docs.aws.amazon.com/appconfig/2019-10-09/APIReference/API_appconfigdata_GetLatestConfiguration.html) to fetch your configuration data. The configuration data is saved to the `mydata.json` file.
```
aws appconfigdata get-latest-configuration \
--configuration-token initial configuration token mydata.json
```
The first call to `GetLatestConfiguration` uses the `ConfigurationToken` obtained from `StartConfigurationSession`. The following information is returned.
```
{
"NextPollConfigurationToken" : next configuration token,
"ContentType" : content type of configuration,
"NextPollIntervalInSeconds" : 60
}
```
Subsequent calls to `GetLatestConfiguration` *must* provide `NextPollConfigurationToken` from the previous response.
```
aws appconfigdata get-latest-configuration \
--configuration-token next configuration token mydata.json
```
**Important**
Note the following important details about the `GetLatestConfiguration` API operation:
The `GetLatestConfiguration` response includes a `Configuration` section that shows the configuration data. The `Configuration` section only appears if the system finds new or updated configuration data. If the system doesn't find new or updated configuration data, then the `Configuration` data is empty.
You receive a new `ConfigurationToken` in every response from `GetLatestConfiguration`.
We recommend tuning the polling frequency of your `GetLatestConfiguration` API calls based on your budget, the expected frequency of your configuration deployments, and the number of targets for a configuration.