diff --git a/master-slave/Makefile b/master-slave/Makefile
index 89f4526..071378b 100644
--- a/master-slave/Makefile
+++ b/master-slave/Makefile
@@ -38,6 +38,9 @@
 ifdef VPC_CIDR
 		$(eval CLUSTER_OPTIONAL_PARAMS := $(CLUSTER_OPTIONAL_PARAMS) ParameterKey=VPCCIDR,ParameterValue=$(VPC_CIDR))
 endif
+ifdef MASTER_MAX_COUNT
+		$(eval CLUSTER_OPTIONAL_PARAMS := $(CLUSTER_OPTIONAL_PARAMS) ParameterKey=MasterMaxCount,ParameterValue=$(MASTER_MAX_COUNT))
+endif
 
 	$(AWS_FC_COMMAND) create-stack \
 		--stack-name $(CLUSTER_STACK_NAME) \
@@ -45,7 +48,6 @@
 		--template-body file://`pwd`/$(CLUSTER_TEMPLATE) \
 		--region $(AWS_REGION) \
 		--parameters \
-		ParameterKey=DesiredCapacity,ParameterValue=$(CLUSTER_DESIRED_CAPACITY) \
 		ParameterKey=ECSKeyName,ParameterValue=$(CLUSTER_KEYS) \
 		ParameterKey=TemplateBucketName,ParameterValue=$(TEMPLATE_BUCKET_NAME) \
 		ParameterKey=InternetGatewayIdProp,ParameterValue=$(INTERNET_GATEWAY_ID) \
diff --git a/master-slave/README.md b/master-slave/README.md
index 2581e05..f08f0f2 100644
--- a/master-slave/README.md
+++ b/master-slave/README.md
@@ -76,14 +76,13 @@
 * `DASHBOARD_STACK_NAME` : Optional. Name of the dashboard stack. `gerrit-dashboard` by default.
 * `MASTER_SUBDOMAIN`: Optional. Name of the master sub domain. `gerrit-master-demo` by default.
 * `SLAVE_SUBDOMAIN`: Optional. Name of the slave sub domain. `gerrit-slave-demo` by default.
-* `CLUSTER_DESIRED_CAPACITY`: Optional. Number of EC2 instances composing the cluster. `1` by default.
 * `GERRIT_MASTER_INSTANCE_ID`: Optional. Identifier for the Gerrit master instance.
 "gerrit-master-slave-MASTER" by default.
 * `GERRIT_SLAVE_INSTANCE_ID`: Optional. Identifier for the Gerrit slave instance.
 "gerrit-master-slave-SLAVE" by default.
 
 *NOTE*: if you are planning to run the monitoring stack, set the
-`CLUSTER_DESIRED_CAPACITY` value to at least 2. The resources provided by
+`MASTER_MAX_COUNT` value to at least 2. The resources provided by
 a single EC2 instance won't be enough for all the services that will be ran*
 
 * `PROMETHEUS_SUBDOMAIN`: Optional. Prometheus subdomain. For example: `<AWS_PREFIX>-prometheus`
diff --git a/master-slave/cf-cluster.yml b/master-slave/cf-cluster.yml
index f2668a2..e56e341 100644
--- a/master-slave/cf-cluster.yml
+++ b/master-slave/cf-cluster.yml
@@ -6,14 +6,9 @@
   TemplateBucketName:
     Description: S3 bucket containing cloudformation templates
     Type: String
-  DesiredCapacity:
+  MasterMaxCount:
+    Description: The maximum number of EC2 instances in the master autoscaling group
     Type: Number
-    Default: '1'
-    Description: Number of EC2 instances to launch in your ECS cluster.
-  MaxSize:
-    Type: Number
-    Default: '6'
-    Description: Maximum number of EC2 instances that can be launched in your ECS cluster.
   ECSAMI:
     Description: AMI ID
     Type: AWS::SSM::Parameter::Value<AWS::EC2::Image::Id>
@@ -77,24 +72,23 @@
           LogGroupName: !Ref AWS::StackName
           RetentionInDays: 14
 
-  # Autoscaling group. This launches the actual EC2 instances that will register
-  # themselves as members of the cluster, and run the docker containers.
-  ECSAutoScalingGroup:
+  MasterASG:
     Type: AWS::AutoScaling::AutoScalingGroup
     Properties:
       VPCZoneIdentifier:
         - !GetAtt ECSTaskNetworkStack.Outputs.PublicSubnetOneRef
-      LaunchConfigurationName: !Ref 'ContainerInstances'
+      LaunchConfigurationName: !Ref 'MasterLaunchConfiguration'
       MinSize: '1'
-      MaxSize: !Ref 'MaxSize'
-      DesiredCapacity: !Ref 'DesiredCapacity'
+      MaxSize: !Ref MasterMaxCount
+      DesiredCapacity: '1'
     CreationPolicy:
       ResourceSignal:
         Timeout: PT15M
     UpdatePolicy:
       AutoScalingReplacingUpdate:
         WillReplace: 'true'
-  ContainerInstances:
+
+  MasterLaunchConfiguration:
     Type: AWS::AutoScaling::LaunchConfiguration
     Properties:
       ImageId: !Ref 'ECSAMI'
@@ -106,9 +100,10 @@
         Fn::Base64: !Sub |
           #!/bin/bash -xe
           echo ECS_CLUSTER=${ECSCluster} >> /etc/ecs/ecs.config
+          echo ECS_INSTANCE_ATTRIBUTES={\"target_group\":\"master\"} >> /etc/ecs/ecs.config
           # Make sure latest version of the helper scripts are installed as per recommendation:
           # https://github.com/awsdocs/aws-cloudformation-user-guide/blob/master/doc_source/cfn-helper-scripts-reference.md#using-the-latest-version
-          yum install -y aws-cfn-bootstrap
+          yum install -y aws-cfn-bootstrap wget
           # Get the CloudWatch Logs agent
           echo -e "
             {\"logs\":
@@ -116,26 +111,6 @@
                 {\"files\":
                   {\"collect_list\":
                     [
-                      {\"file_path\": \"/var/lib/docker/volumes/gerrit-logs-slave/_data/httpd_log\",
-                      \"log_group_name\": \"${AWS::StackName}\",
-                      \"log_stream_name\": \"${EnvironmentName}/{instance_id}/slave/httpd_log\",
-                      \"timezone\": \"UTC\"
-                      },
-                      {\"file_path\": \"/var/lib/docker/volumes/gerrit-logs-slave/_data/sshd_log\",
-                      \"log_group_name\": \"${AWS::StackName}\",
-                      \"log_stream_name\": \"${EnvironmentName}/{instance_id}/slave/sshd_log\",
-                      \"timezone\": \"UTC\"
-                      },
-                      {\"file_path\": \"/var/lib/docker/volumes/gerrit-logs-slave/_data/gc_log\",
-                      \"log_group_name\": \"${AWS::StackName}\",
-                      \"log_stream_name\": \"${EnvironmentName}/{instance_id}/slave/gc_log\",
-                      \"timezone\": \"UTC\"
-                      },
-                      {\"file_path\": \"/var/lib/docker/volumes/gerrit-logs-slave/_data/audit_log\",
-                      \"log_group_name\": \"${AWS::StackName}\",
-                      \"log_stream_name\": \"${EnvironmentName}/{instance_id}/slave/audit_log\",
-                      \"timezone\": \"UTC\"
-                      },
                       {\"file_path\": \"/var/lib/docker/volumes/gerrit-logs-master/_data/replication_log\",
                       \"log_group_name\": \"${AWS::StackName}\",
                       \"log_stream_name\": \"${EnvironmentName}/{instance_id}/master/replication_log\",
@@ -167,12 +142,89 @@
               }
             }" >> /home/ec2-user/gerritlogsaccess.json
           # Install the CloudWatch Logs agent
-          yum install -y wget
           wget https://s3.amazonaws.com/amazoncloudwatch-agent/centos/amd64/latest/amazon-cloudwatch-agent.rpm
           rpm -U ./amazon-cloudwatch-agent.rpm
           /opt/aws/amazon-cloudwatch-agent/bin/amazon-cloudwatch-agent-ctl -a fetch-config -m ec2 -c file:/home/ec2-user/gerritlogsaccess.json -s
           # Signal to CloudFormation aws-cfn-bootstrap has been correctly updated
-          /opt/aws/bin/cfn-signal -e $? --stack ${AWS::StackName} --resource ECSAutoScalingGroup --region ${AWS::Region}
+          /opt/aws/bin/cfn-signal -e $? --stack ${AWS::StackName} --resource MasterASG --region ${AWS::Region}
+
+
+  ReplicaASG:
+    Type: AWS::AutoScaling::AutoScalingGroup
+    Properties:
+      VPCZoneIdentifier:
+        - !GetAtt ECSTaskNetworkStack.Outputs.PublicSubnetOneRef
+      LaunchConfigurationName: !Ref 'ReplicaLaunchConfiguration'
+      MinSize: '1'
+      MaxSize: '1'
+      DesiredCapacity: '1'
+    CreationPolicy:
+      ResourceSignal:
+        Timeout: PT15M
+    UpdatePolicy:
+      AutoScalingReplacingUpdate:
+        WillReplace: 'true'
+
+  ReplicaLaunchConfiguration:
+    Type: AWS::AutoScaling::LaunchConfiguration
+    Properties:
+      ImageId: !Ref 'ECSAMI'
+      SecurityGroups: [!Ref 'EcsHostSecurityGroup']
+      InstanceType: !Ref 'InstanceType'
+      IamInstanceProfile: !Ref 'EC2InstanceProfile'
+      KeyName: !Ref ECSKeyName
+      UserData:
+        Fn::Base64: !Sub |
+          #!/bin/bash -xe
+          echo ECS_CLUSTER=${ECSCluster} >> /etc/ecs/ecs.config
+          echo ECS_INSTANCE_ATTRIBUTES={\"target_group\":\"replica\"} >> /etc/ecs/ecs.config
+
+          # Make sure latest version of the helper scripts are installed as per recommendation:
+          # https://github.com/awsdocs/aws-cloudformation-user-guide/blob/master/doc_source/cfn-helper-scripts-reference.md#using-the-latest-version
+          yum install -y aws-cfn-bootstrap wget
+          # Get the CloudWatch Logs agent
+          echo -e "
+            {\"logs\":
+              {\"logs_collected\":
+                {\"files\":
+                  {\"collect_list\":
+                    [
+                      {\"file_path\": \"/var/lib/docker/volumes/gerrit-logs-slave/_data/replication_log\",
+                      \"log_group_name\": \"${AWS::StackName}\",
+                      \"log_stream_name\": \"${EnvironmentName}/{instance_id}/slave/replication_log\",
+                      \"timezone\": \"UTC\"
+                      },
+                      {\"file_path\": \"/var/lib/docker/volumes/gerrit-logs-slave/_data/httpd_log\",
+                      \"log_group_name\": \"${AWS::StackName}\",
+                      \"log_stream_name\": \"${EnvironmentName}/{instance_id}/slave/httpd_log\",
+                      \"timezone\": \"UTC\"
+                      },
+                      {\"file_path\": \"/var/lib/docker/volumes/gerrit-logs-slave/_data/sshd_log\",
+                      \"log_group_name\": \"${AWS::StackName}\",
+                      \"log_stream_name\": \"${EnvironmentName}/{instance_id}/slave/sshd_log\",
+                      \"timezone\": \"UTC\"
+                      },
+                      {\"file_path\": \"/var/lib/docker/volumes/gerrit-logs-slave/_data/gc_log\",
+                      \"log_group_name\": \"${AWS::StackName}\",
+                      \"log_stream_name\": \"${EnvironmentName}/{instance_id}/slave/gc_log\",
+                      \"timezone\": \"UTC\"
+                      },
+                      {\"file_path\": \"/var/lib/docker/volumes/gerrit-logs-slave/_data/audit_log\",
+                      \"log_group_name\": \"${AWS::StackName}\",
+                      \"log_stream_name\": \"${EnvironmentName}/{instance_id}/slave/audit_log\",
+                      \"timezone\": \"UTC\"
+                      }
+                    ]
+                  }
+                }
+              }
+            }" >> /home/ec2-user/gerritlogsaccess.json
+          # Install the CloudWatch Logs agent
+          wget https://s3.amazonaws.com/amazoncloudwatch-agent/centos/amd64/latest/amazon-cloudwatch-agent.rpm
+          rpm -U ./amazon-cloudwatch-agent.rpm
+          /opt/aws/amazon-cloudwatch-agent/bin/amazon-cloudwatch-agent-ctl -a fetch-config -m ec2 -c file:/home/ec2-user/gerritlogsaccess.json -s
+          # Signal to CloudFormation aws-cfn-bootstrap has been correctly updated
+          /opt/aws/bin/cfn-signal -e $? --stack ${AWS::StackName} --resource ReplicaASG --region ${AWS::Region}
 
   EC2InstanceProfile:
     Type: AWS::IAM::InstanceProfile
diff --git a/master-slave/cf-service-master.yml b/master-slave/cf-service-master.yml
index 3c1f39b..ba08b97 100644
--- a/master-slave/cf-service-master.yml
+++ b/master-slave/cf-service-master.yml
@@ -228,6 +228,9 @@
             TaskRoleArn: !GetAtt ECSTaskExecutionRoleStack.Outputs.TaskExecutionRoleRef
             ExecutionRoleArn: !GetAtt ECSTaskExecutionRoleStack.Outputs.TaskExecutionRoleRef
             NetworkMode: bridge
+            PlacementConstraints:
+              - Expression: !Sub 'attribute:target_group == master'
+                Type: "memberOf"
             ContainerDefinitions:
                 - Name: !Ref GerritServiceName
                   Essential: true
diff --git a/master-slave/cf-service-slave.yml b/master-slave/cf-service-slave.yml
index 80014f6..44f19c2 100644
--- a/master-slave/cf-service-slave.yml
+++ b/master-slave/cf-service-slave.yml
@@ -225,6 +225,9 @@
             TaskRoleArn: !GetAtt ECSTaskExecutionRoleStack.Outputs.TaskExecutionRoleRef
             ExecutionRoleArn: !GetAtt ECSTaskExecutionRoleStack.Outputs.TaskExecutionRoleRef
             NetworkMode: bridge
+            PlacementConstraints:
+              - Expression: !Sub 'attribute:target_group == replica'
+                Type: "memberOf"
             ContainerDefinitions:
                 - Name: !Ref GerritServiceName
                   Essential: true
diff --git a/master-slave/setup.env.template b/master-slave/setup.env.template
index d87bbaa..c14f6a8 100644
--- a/master-slave/setup.env.template
+++ b/master-slave/setup.env.template
@@ -1,4 +1,4 @@
-CLUSTER_DESIRED_CAPACITY:=1
+MASTER_MAX_COUNT=2
 CLUSTER_INSTANCE_TYPE:=m4.xlarge
 SERVICE_MASTER_STACK_NAME:=$(AWS_PREFIX)-service-master
 SERVICE_SLAVE_STACK_NAME:=$(AWS_PREFIX)-service-slave