[beginner] Install third party application on AWS EC2

In this solution I installed Mattermost application using open source package

Following are the brief steps implemented in this solution.

Create Custom VPC to build the solution.
Implement 2 different subnets (one public and the other private) in a this VPC
Implement Route table and make connection to internet gateway for internet capability to public subnet.
Implement NAT Instance along with another custom route entry which will allow private instance to connect to internet securely.
Allow Public subnet only to connect to private instance like a bastion host.
Install and configure MySQL on an Ubuntu 18.04 instance on the private subnet.
Install and configure Mattermost on an Ubuntu 18.04 instance on the public subnet.
Configure the security groups to allow the ports as shown in the architecture.
Test the installation by accessing the IP of the public instance in a browser via the port 8065.
Monitor application in cloudwatch.

Complete solution is published here