Event source mapping for AWS stream-based services

Figure 17.3 explains the way a custom application writes a record to a Kinesis stream and the way Lambda polls the stream:

Figure 17.3: Event source mapping for AWS stream-based services

Reference URL: https://docs.aws.amazon.com/lambda/latest/dg/images/kinesis-pull-10.png

The steps for the preceding figure are as follows:

1. The custom application writes records to an Amazon Kinesis stream.
2. At the same time, AWS Lambda continuously keeps polling the stream. As soon as it detects a new record on the stream, it invokes the AWS Lambda function. Based on the event configuration, it decides which Lambda function is to execute against which event source.
3. It verifies that the attached IAM permission policy to the Lambda function allows it to poll the stream. If it is not true, then the AWS Lambda function is not invoked.

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