JSON get's converted to Base64

[awslabs]

JSON get's converted to Base64

[MacInnis]

This is expected behavior. The AWS SDK for JavaScript (used in this project) automatically base64-encodes the data before it sends it to Kinesis Data Streams or Kinesis Data Firehose. The API documentation for Kinesis Data Streams mentions that input data should be base64-encoded: https://docs.aws.amazon.com/kinesis/latest/APIReference/API_PutRecord.html

Data consumers need to base64 decode the data to obtain the original record. This is mentioned in the example in this documentation: https://docs.aws.amazon.com/streams/latest/dev/fundamental-stream.html