CloudWatch Events allow subscription to AWS API calls, and direction of these events into Kinesis Streams. This allows a unified, near real-time stream for all API calls, which can be analyzed with any tool(s) of your choosing downstream.
http://docs.aws.amazon.com/AmazonCloudWatch/latest/DeveloperGuide/EventTypes.html#api_e vent_ty pe

Explanation
Amazon Dasticsearch Service makes it easy to deploy, operate, and scale dasticsearch for log analytics, full
text search, application monitoring, and more. Amazon
Oasticsearch Service is a fully managed service that delivers Dasticsearch's easy-to-use APIs and real-time
capabilities along with the availability, scalability, and
security required by production workloads. The service offers built-in integrations with Kibana, Logstash, and
AWS services including Amazon Kinesis Firehose, AWS
Lambda, and Amazon CloudWatch so that you can go from raw data to actionable insights quickly
For more information on the elastic cache service, please refer to the below link:
* https://aws.amazon.com/elasticsearch-service/

Explanation
AWS Cloud Formation gives developers and systems administrators an easy way to create and manage a
collection of related AWS resources, provisioning and updating them in an orderly and predictable fashion.
You can use AWS Cloud Formation's sample templates or create your own templates to describe the AWS
resources, and any associated dependencies or runtime parameters, required to run your application. You don't
need to figure out the order for provisioning AWS services or the subtleties of making those dependencies
work. Cloud Formation takes care of this for you. After the AWS resources are deployed, you can modify and
update them in a controlled and predictable way, in effect applying version control to your AWS infrastructure
the same way you do with your software. You can also visualize your templates as diagrams and edit them
using a drag-and-drop interface with the AWS CloudFormation Designer.
For more information on Cloudformation, please visit the link:
* https://aws.amazon.com/cloudformation/

https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/continuous-delivery-codepipeline-parameter-override-functions.html

Explanation
The AWS Documentation mentions the following Restores the previously deployed app version. For example,
if you have deployed the app three times and then run Rollback, the server will serve the app from the second
deployment. If you run Rollback again, the server will serve the app from the first deployment. By default,
AWS OpsWorks Stacks stores the five most recent deployments, which allows you to roll back up to four
versions. If you exceed the number of stored versions, the command fails and leaves the oldest version in
place.
For more information on Opswork app deployment, please visit the below U RL:
* http://docs.aws.amazon.com/opsworks/latest/userguide/workingapps-deploying.
html