ECS Fargate Mongo Express client is not accessible from public port 8081

Question

As the name suggests, I've setup a simple application stack with a Java (Spring Boot) backend and another Mongo Express client with ECS Fargate. The Mongo DB is setup in a completely separate host and it's accessible from the Fargate stack without issue. So far everything is working fine - both Java and Mongo Express clients connect to the database successfully during start up (I check the logs). I have setup correct inbound rules in the SG (security group) allowing both ports for Java and Mongo Express.

However, I can only access the Java app via its port (8080) and Mongo Express port (8081) is hanging when I try to connect.

Do I need to setup a reverse proxy or some sort (Nginx?) to route network to Mongo Express? As far as I know, I could directly communicate to the port (8081 in this case) without Nginx as long as a routing method is implemented in the application, like in Express server. I don't know much about Mongo Express or Node.js but I can see from documentation it needs Node.js to run.

Anyone got any idea why I cannot access the Mongo Express client using http://<public_ip>:<port>? I appreciate any clue so I can think through to figure this out.

Below are the ECS task definition and service definition.

Task Definition

{
    "family": "service-connect-backend-task",
    "executionRoleArn": "*************************",
    "taskRoleArn": "************************",
    "networkMode": "awsvpc",
    "containerDefinitions": [
      {
        "name": "java",
        "image": "********************************",
        "cpu": 256,
        "memory": 512,
        "portMappings": [
          {
              "name": "java-8080",
              "containerPort": 8080,
              "protocol": "tcp",
              "appProtocol": "http"
          }
        ],
        "essential": true,
        "environment": [
          {
            "name": "DB_HOST",
            "value": "****************"
          },
          {
            "name": "SPRING_ACTIVE_PROFILE",
            "value": "develop"
          }
        ],
        "logConfiguration": {
          "logDriver": "awslogs",
          "options": {
              "awslogs-create-group": "true",
              "awslogs-group": "/ecs/service-connect-java-backend",
              "awslogs-region": "********", 
              "awslogs-stream-prefix": "java"
          }
        },
        "healthCheck": {
          "command": [
            "CMD-SHELL",
            "echo HealthOk"
          ],
          "interval": 5,
          "timeout": 2,
          "retries": 3,
          "startPeriod": 10
        }
      },
      {
        "name": "mongo-express",
        "image": "mongo-express",
        "cpu": 256,
        "memory": 512,
        "portMappings": [
          {
              "name": "mongoexpress-8081",
              "containerPort": 8081,
              "protocol": "tcp", 
              "appProtocol": "http"
          }
        ],
        "essential": true,
        "environment": [
          {
            "name": "ME_CONFIG_BASICAUTH_PASSWORD",
            "value": "****************"
          },
          {
            "name": "ME_CONFIG_MONGODB_AUTH_USERNAME",
            "value": " ****************"
          },
          {
            "name": "ME_CONFIG_MONGODB_SERVER",
            "value": "****************"
          },
          {
            "name": "ME_CONFIG_BASICAUTH_USERNAME",
            "value": "****************"
          },
          {
            "name": "ME_CONFIG_MONGODB_AUTH_PASSWORD",
            "value": "****************"
          },
          {
            "name": "ME_CONFIG_MONGODB_AUTH_DATABASE",
            "value": "admin"
          }
        ],
        "logConfiguration": {
          "logDriver": "awslogs",
          "options": {
              "awslogs-create-group": "true",
              "awslogs-group": "/ecs/service-connect-mongo-express",
              "awslogs-region": "******", 
              "awslogs-stream-prefix": "mongo-express"
          }
        }
      }
    ],
    "cpu": "512",
    "memory": "1024"
}

Service Definition

{
    "cluster": "ce-develop-cluster",
    "deploymentConfiguration": {
        "maximumPercent": 200,
        "minimumHealthyPercent": 100
    },
    "deploymentController": {
        "type": "ECS"
    },
    "desiredCount": 1,
    "enableECSManagedTags": true,
    "enableExecuteCommand": true,
    "launchType": "FARGATE",
    "networkConfiguration": {
        "awsvpcConfiguration": {
            "assignPublicIp": "ENABLED",
            "securityGroups": [
                "****************"
            ],
            "subnets": [
                "****************"
            ]
        }
    },
    "platformVersion": "LATEST",
    "propagateTags": "SERVICE",
    "serviceName": "service-connect-backend-service",
    "serviceConnectConfiguration": {
        "enabled": true,
        "services": [
            {
                "portName": "java-8080",
                "clientAliases": [
                    {
                        "dnsName": "backend",
                        "port": 80
                    }
                ]
            },
            {
                "portName": "mongoexpress-8081",
                "clientAliases": [
                    {
                        "dnsName": "mongo-express",
                        "port": 81
                    }
                ]
            }
        ],
        "logConfiguration": {
            "logDriver": "awslogs",
            "options": {
                "awslogs-create-group": "true",
                "awslogs-group": "/ecs/service-connect-backend-proxy",
                "awslogs-region": "********",
                "awslogs-stream-prefix": "service-connect-backend-proxy"
            }
        }
    },
    "taskDefinition": "service-connect-backend-task"
}

Edit 1: I've used ECS Service Connect here aiming for some more applications to be added to the stack in future - like a React client that can talk to the backend via service connect namespace. But I don't know whether it has an impact when accessing a container directly from internet.

Edit 2: I disabled the service connect and updated the service and I still get the same result.