AWS Network 102 – Connection

  • VPC Endpoints: Privately connect your VPC to supported AWS services. Interface Endpoint (PrivateLink), Gateway Endpoint (S3, DynamoDB)
  • VPC Peering: Networking connection between two VPCs that enables you to route traffic between them using private IPv4 addresses or IPv6 addresses. A VPC peering connection helps you to facilitate the transfer of data. You can establish peering relationships between VPCs across different AWS Regions (also called Inter-Region VPC Peering)
  • VPN:secure connections between your on-premises networks, remote offices, client devices, and the AWS global network.AWS Site-to-Site VPN creates encrypted tunnels between your network and your Amazon VPC or AWS Transit Gateways. For managing remote access, AWS Client VPN connects your users to AWS or on-premises resources using a free VPN software client.
  • Direct Connect:securely connect your AWS environment to your on-premises data center or office location over a standard 1 gigabit or 10 gigabit Ethernet fiber-optic connection. AWS Direct Connect offers dedicated high speed, low latency connection, which bypasses internet service providers in your network path.
  • Nat Gateway: enable instances in a private subnet to connect to the internet or other AWS services, but prevent the internet from initiating a connection with those instances.NAT gateways are not supported for IPv6 traffic—use an outbound-only (egress-only) internet gateway instead.To create a NAT gateway, you must specify the public subnet in which the NAT gateway should reside.You must also specify an Elastic IP address to associate with the NAT gateway when you create it.
  • Egress-only internet gateways:An egress-only internet gateway is a horizontally scaled, redundant, and highly available VPC component that allows outbound communication over IPv6 from instances in your VPC to the internet, and prevents the internet from initiating an IPv6 connection with your instances.
  • Global Accelerator: improves the availability and performance of your applications with local or global users. It provides static IP addresses that act as a fixed entry point to your application endpoints in a single or multiple AWS Regions, such as your Application Load Balancers, Network Load Balancers or Amazon EC2 instances.
  • Transit Gateway: connects VPCs and on-premises networks through a central hub.Inter-Region peering connects AWS Transit Gateways together using the AWS global network. Your data is automatically encrypted, and never travels over the public internet.

AWS API Gateway – Troubleshooting -blocked by CORS policy

Error: has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource.

Solution: Update your lambda handler function (aws doc)

exports.handler = async (event) => {
    const response = {
        statusCode: 200,
        headers: {
            "Access-Control-Allow-Headers" : "Content-Type",
            "Access-Control-Allow-Origin": "",
            "Access-Control-Allow-Methods": "OPTIONS,POST,GET"
        body: JSON.stringify('Hello from Lambda!'),
    return response;

AWS Basic – Network 101

Here are the AWS Networking knowledges that are fundamental for cloud computing.

Region: (e.g. us-east-1)

AWS has the concept of a Region, which is a physical location around the world where we cluster data centers.

Each AWS Region is designed to be isolated from the other AWS Regions. This design achieves the greatest possible fault tolerance and stability.


The Amazon Virtual Private Cloud (Amazon VPC) service lets you provision a private, isolated section of the AWS Cloud where you can launch AWS services and other resources in a virtual network that you define.

Availability Zone: (e.g: us-east-1a)

An Availability Zone (AZ) is one or more discrete data centers with redundant power, networking, and connectivity in an AWS Region. AZ’s give customers the ability to operate production applications and databases that are more highly available, fault tolerant, and scalable than would be possible from a single data center.


Separate subnets for unique routing requirements. AWS recommends using public subnets for external-facing resources and private subnets for internal resources. For each Availability Zone, this Quick Start provisions one public subnet and one private subnet by default.

Internet Gateway:

An internet gateway is an access point through which your resources can access the internet and be accessed from the internet.

NAT Gateway:

A NAT gateway can route outgoing traffic from private subnets to the internet.

Route 53:

Amazon Route 53 is the DNS available for your AWS resources.

AWS Cognito + MP JWT RBAC + Quarkus

In this blog, we will try to build a Role-Based-Access-Control (RBAC) with Quarkus, MicroProile JWT RBAC and AWS Cognito.

AWS Cognito will create JWT token and RSA Public Key Distribution. Quarkus, MicroProile are responsible for Java Server-side API endpoints.

Useful links:

Eclipse MicroProfile – JWT RBAC Security (MP-JWT)


  • Create AWS Cognito User Pool and then in this User Pool create a User and Group. Here we use “Cognito Groups” as “User Roles”.
  • Create an AWS Cognito Identity Pool and get an identity pool Id , eg "eu-central-1_xxxxx". This Cognito Identity Pool will be the JWT Issuer and we could find the RSA Publicy Key under ""
  • Create the endpoint by using Quarkus, for example:
public class OrderResource {

    @RolesAllowed({"USER", "ADMIN"})
    public Response list(){
        return Response.ok(Arrays.asList("Order1", "Order2")).build();

Most important since the default group claim in MP-JWT is “groups” but the Cognito group claim is “cognito:groups” so we need config a mapping.


Other necessary configs:




For testing and getting a cognito jwt token you could try aws cli:

aws cognito-idp admin-initiate-auth --region eu-central-1 --cli-input-json file://auth.json

Then you put that token in the HTTP header “Authorization” and begins with “Bearer ” for example:

curl -X GET \
https://example/orders \
-H 'Authorization: Bearer YOUR_JWT_TOKEN' \

There you are the integration Quarkus + MP JWT and AWS Cognito. Enjoy!

This blog is under category “API“.

AWS S3 SDK Java Feedback

  • Verify if Bucket already exists

call the doesBucketExist method

  • Create Subdirectory (folder): using key

PutObjectRequest request = new PutObjectRequest(bucketName, "folder/", new File(fileName));

  • Remove all the files under folder:

    using key like : folder/

  • Using Presigned Url to share object (public url)

Often we need upload a file (image) to S3 and get a tempory public URL of this object. (Be careful, you should always set private-access to this object)

We could use Presigned-url with an expiration period.

Code Example