# Examples: Invoking Lambda functions from your RDS for PostgreSQL DB instance
Following, you can find several examples of calling the [aws\$1lambda.invoke](PostgreSQL-Lambda-functions.md#aws_lambda.invoke) function. Most of the examples use the composite structure `aws_lambda_arn_1` that you create in [Step 4: Use Lambda helper functions with your RDS for PostgreSQL DB instance (Optional)](PostgreSQL-Lambda.md#PostgreSQL-Lambda-specify-function) to simplify passing the function details. For an example of asynchronous invocation, see [Example: Asynchronous (Event) invocation of Lambda functions](#PostgreSQL-Lambda-Event). All the other examples listed use synchronous invocation.
To learn more about Lambda invocation types, see [Invoking Lambda functions](https://docs.aws.amazon.com/lambda/latest/dg/lambda-invocation.html) in the *AWS Lambda Developer Guide*. For more information about `aws_lambda_arn_1`, see [aws\$1commons.create\$1lambda\$1function\$1arn](PostgreSQL-Lambda-functions.md#aws_commons.create_lambda_function_arn).
**Topics**
+ [Example: Synchronous (RequestResponse) invocation of Lambda functions](#PostgreSQL-Lambda-RequestResponse)
+ [Example: Asynchronous (Event) invocation of Lambda functions](#PostgreSQL-Lambda-Event)
+ [Example: Capturing the Lambda execution log in a function response](#PostgreSQL-Lambda-log-response)
+ [Example: Including client context in a Lambda function](#PostgreSQL-Lambda-client-context)
+ [Example: Invoking a specific version of a Lambda function](#PostgreSQL-Lambda-function-version)
## Example: Synchronous (RequestResponse) invocation of Lambda functions
Following are two examples of a synchronous Lambda function invocation. The results of these `aws_lambda.invoke` function calls are the same.
```
SELECT * FROM aws_lambda.invoke('aws_lambda_arn_1', '{"body": "Hello from Postgres!"}'::json);
```
```
SELECT * FROM aws_lambda.invoke('aws_lambda_arn_1', '{"body": "Hello from Postgres!"}'::json, 'RequestResponse');
```
The parameters are described as follows:
+ `:'aws_lambda_arn_1'` – This parameter identifies the composite structure created in [Step 4: Use Lambda helper functions with your RDS for PostgreSQL DB instance (Optional)](PostgreSQL-Lambda.md#PostgreSQL-Lambda-specify-function), with the `aws_commons.create_lambda_function_arn` helper function. You can also create this structure inline within your `aws_lambda.invoke` call as follows.
```
SELECT * FROM aws_lambda.invoke(aws_commons.create_lambda_function_arn('my-function', 'aws-region'),
'{"body": "Hello from Postgres!"}'::json
);
```
+ `'{"body": "Hello from PostgreSQL!"}'::json` – The JSON payload to pass to the Lambda function.
+ `'RequestResponse'` – The Lambda invocation type.
## Example: Asynchronous (Event) invocation of Lambda functions
Following is an example of an asynchronous Lambda function invocation. The `Event` invocation type schedules the Lambda function invocation with the specified input payload and returns immediately. Use the `Event` invocation type in certain workflows that don't depend on the results of the Lambda function.
```
SELECT * FROM aws_lambda.invoke('aws_lambda_arn_1', '{"body": "Hello from Postgres!"}'::json, 'Event');
```
## Example: Capturing the Lambda execution log in a function response
You can include the last 4 KB of the execution log in the function response by using the `log_type` parameter in your `aws_lambda.invoke` function call. By default, this parameter is set to `None`, but you can specify `Tail` to capture the results of the Lambda execution log in the response, as shown following.
```
SELECT *, select convert_from(decode(log_result, 'base64'), 'utf-8') as log FROM aws_lambda.invoke(:'aws_lambda_arn_1', '{"body": "Hello from Postgres!"}'::json, 'RequestResponse', 'Tail');
```
Set the [aws\$1lambda.invoke](PostgreSQL-Lambda-functions.md#aws_lambda.invoke) function's `log_type` parameter to `Tail` to include the execution log in the response. The default value for the `log_type` parameter is `None`.
The `log_result` that's returned is a `base64` encoded string. You can decode the contents using a combination of the `decode` and `convert_from` PostgreSQL functions.
For more information about `log_type`, see [aws\$1lambda.invoke](PostgreSQL-Lambda-functions.md#aws_lambda.invoke).
## Example: Including client context in a Lambda function
The `aws_lambda.invoke` function has a `context` parameter that you can use to pass information separate from the payload, as shown following.
```
SELECT *, convert_from(decode(log_result, 'base64'), 'utf-8') as log FROM aws_lambda.invoke(:'aws_lambda_arn_1', '{"body": "Hello from Postgres!"}'::json, 'RequestResponse', 'Tail');
```
To include client context, use a JSON object for the [aws\$1lambda.invoke](PostgreSQL-Lambda-functions.md#aws_lambda.invoke) function's `context` parameter.
For more information about the `context` parameter, see the [aws\$1lambda.invoke](PostgreSQL-Lambda-functions.md#aws_lambda.invoke) reference.
## Example: Invoking a specific version of a Lambda function
You can specify a particular version of a Lambda function by including the `qualifier` parameter with the `aws_lambda.invoke` call. Following, you can find an example that does this using `'custom_version'` as an alias for the version.
```
SELECT * FROM aws_lambda.invoke('aws_lambda_arn_1', '{"body": "Hello from Postgres!"}'::json, 'RequestResponse', 'None', NULL, 'custom_version');
```
You can also supply a Lambda function qualifier with the function name details instead, as follows.
```
SELECT * FROM aws_lambda.invoke(aws_commons.create_lambda_function_arn('my-function:custom_version', 'us-west-2'),
'{"body": "Hello from Postgres!"}'::json);
```
For more information about `qualifier` and other parameters, see the [aws\$1lambda.invoke](PostgreSQL-Lambda-functions.md#aws_lambda.invoke) reference.