diff --git a/README.md b/README.md
index fdb6026..7a43eda 100644
--- a/README.md
+++ b/README.md
@@ -63,6 +63,7 @@ alb_ssl_policy: "ELBSecurityPolicy-2016-08"
 alb_certificate_arn: "arn:aws:acm:us-east-1:290379793816:certificate/6d1bab74-fb46-4244-aab2-832bf519ab24"
 root_block_size: 120
 pool_size: 30
+elixir_version: v1.7.4
 secret_key_base: "TPGMvGK0iIwlXBQuQDA5KRqk77VETbEBlG4gAWeb93TvBsYAjvoAvdODMd6ZeguPwf2YTRY3n7uvxXzQP4WayQ=="
 new_relic_app_name: ""
 new_relic_license_key: ""
@@ -110,7 +111,9 @@ chain_db_instance_class:
 chain_db_storage:
    mychain: "200"
 chain_db_storage_type:
-   mychain: "gp2"
+   chain: "io1"
+chain_db_iops:
+   chain: "1000"
 chain_db_version:
    mychain: "10.5" 
 ```
@@ -121,7 +124,12 @@ chain_db_version:
 - `bucket` and `dynamodb_table` represents the name of AWS resources that will be used for Terraform state management;
 - If `ec2_ssh_key_content` variable is not empty, Terraform will try to create EC2 SSH key with the `ec2_ssh_key_name` name. Otherwise, the existing key with `ec2_ssh_key_name` name will be used;
 - `instance_type` defines a size of the Blockscout instance that will be launched during the deployment process;
-- `vpc_cidr`, `public_subnet_cidr`, `db_subnet_cidr` represents the network configuration for the deployment. Usually you want to leave it as is. However, if you want to modify it, please, expect that `db_subnet_cidr` represents not a single network, but a group of networks united with one CIDR block that will be divided during the deployment. For details, see [subnets.tf](https://github.com/ArseniiPetrovich/blockscout-terraform/blob/master/roles/main_infra/files/subnets.tf#L35) for details;
+- `vpc_cidr`, `public_subnet_cidr`, `db_subnet_cidr` represents the network configuration for the deployment. Usually you want to leave it as is. However, if you want to modify it, please, expect that `db_subnet_cidr` represents not a single network, but a group of networks started with defined CIDR block increased by 8 bits. 
+Example:
+  Number of networks: 2
+  `db_subnet_cidr`: "10.0.1.0/16"
+  Real networks: 10.0.1.0/24 and 10.0.2.0/24
+    
 - An internal DNS zone with`dns_zone_name` name will be created to take care of BlockScout internal communications;
 - `prefix` - is a unique tag to use for provisioned resources (5 alphanumeric chars or less);
 - The name of a IAM key pair to use for EC2 instances, if you provide a name which
diff --git a/clean.yml b/clean.yml
new file mode 100644
index 0000000..802f305
--- /dev/null
+++ b/clean.yml
@@ -0,0 +1,12 @@
+- name: Clean TF cache
+  hosts: localhost
+  tasks:
+    - name: Clean TF cache
+      file:
+        state: absent
+        path: "{{ item }}"
+      with_items:
+        - roles/main_infra/files/.terraform
+        - roles/main_infra/files/terraform.tfstate.d
+        - roles/main_infra/files/main.tfvars
+        - roles/main_infra/files/backend.tfvars
diff --git a/group_vars/all.yml.example b/group_vars/all.yml.example
index 7b5a27a..f3dc24a 100644
--- a/group_vars/all.yml.example
+++ b/group_vars/all.yml.example
@@ -26,6 +26,9 @@ instance_type: "m5.large"
 ## VPC containing Blockscout resources will be created as following:
 vpc_cidr: "10.0.0.0/16"
 public_subnet_cidr: "10.0.0.0/24"
+# This variable should be interpreted as following:
+# Variable: 10.0.1.0/16
+# Real networks: 10.0.1+{{ number of chain starting with 0 }}.0/24
 db_subnet_cidr: "10.0.1.0/16"
 
 ## Internal DNS zone will looks like:
@@ -55,6 +58,9 @@ secret_key_base: "TPGMvGK0iIwlXBQuQDA5KRqk77VETbEBlG4gAWeb93TvBsYAjvoAvdODMd6Zeg
 new_relic_app_name: ""
 new_relic_license_key: ""
 
+## The following variable represents the elixir version that will be used to run BlockScout instance. Will be used to download the Elixir at the following link: https://github.com/elixir-lang/elixir/releases/download/{{ elixir_version }}/Precompiled.zip
+elixir_version: "v1.7.4"
+
 # Network related variables
 ## This variable represents network RPC endpoint: 
 chains:
@@ -163,6 +169,11 @@ chain_db_storage_type:
   core: "io1"
   sokol: "gp2"
 
+# This should be set only if chain_db_storage is set to io1
+#chain_db_iops:
+#  core: "1000"
+#  sokol: "1500"
+
 # Blockscout uses Postgres as the DB engine. This variable describes the Postgres version used in each particular chain.
 chain_db_version:
   core: "10.5"
diff --git a/roles/check/tasks/main.yml b/roles/check/tasks/main.yml
index 55166ce..fe6107c 100644
--- a/roles/check/tasks/main.yml
+++ b/roles/check/tasks/main.yml
@@ -3,6 +3,12 @@
     msg: "The prefix '{{ prefix }}' is invalid. It must consist only of the lowercase characters a-z and digits 0-9, and must be between 3 and 5 characters long."
   when: prefix|length < 3 or prefix|length > 5 or prefix is not match("^[a-z0-9]+$")
 
+- name: Check chain names
+  fail:
+    msg: "The prefix '{{ item }}' is invalid. It must consist only of the lowercase characters a-z and digits 0-9, and must not more than 5 characters long."
+  when: item.key|length > 5 or item.key is not match("^[a-z0-9]+$")
+  with_dict: "{{ chains }}"
+
 - name: Check if terraform is installed
   command: which terraform
   register: terraform_status
diff --git a/roles/main_infra/files/config.tf b/roles/main_infra/files/config.tf
index baf132c..ddaabbf 100644
--- a/roles/main_infra/files/config.tf
+++ b/roles/main_infra/files/config.tf
@@ -1,3 +1,10 @@
+resource "aws_ssm_parameter" "elixir_version" {
+  count = "${var.new_relic_license_key == "" ? 0 : length(var.chains)}"
+  name  = "/${var.prefix}/${element(keys(var.chains),count.index)}/elixir_version"
+  value = "${var.elixir_version}"
+  type  = "String"
+}
+
 resource "aws_ssm_parameter" "block_transformer" {
   count = "${length(var.chains)}"
   name  = "/${var.prefix}/${element(keys(var.chains),count.index)}/block_transformer"
diff --git a/roles/main_infra/files/libexec/init.sh b/roles/main_infra/files/libexec/init.sh
index beaf433..e0fe64b 100755
--- a/roles/main_infra/files/libexec/init.sh
+++ b/roles/main_infra/files/libexec/init.sh
@@ -135,9 +135,10 @@ wget http://packages.erlang-solutions.com/site/esl/esl-erlang/FLAVOUR_1_general/
 yum install -y wxGTK-devel unixODBC-devel >"$LOG"
 yum install -y esl-erlang_21.1-1~centos~7_amd64.rpm >"$LOG"
 
+ELIXIR_VERSION="$(get_param 'elixir_version')"
 log "Installing Elixir to /opt/elixir.."
 mkdir -p /opt/elixir
-wget https://github.com/elixir-lang/elixir/releases/download/v1.7.4/Precompiled.zip >"$LOG"
+wget https://github.com/elixir-lang/elixir/releases/download/${ELIXIR_VERSION}/Precompiled.zip >"$LOG"
 unzip Precompiled.zip -d /opt/elixir >"$LOG"
 log "Elixir installed successfully!"
 
diff --git a/roles/main_infra/files/rds.tf b/roles/main_infra/files/rds.tf
index 9499e19..1c2def9 100644
--- a/roles/main_infra/files/rds.tf
+++ b/roles/main_infra/files/rds.tf
@@ -14,6 +14,8 @@ resource "aws_db_instance" "default" {
   vpc_security_group_ids = ["${aws_security_group.database.id}"]
   db_subnet_group_name   = "${aws_db_subnet_group.database.id}"
   apply_immediately      = true
+  iops                   = "${lookup(var.chain_db_iops,element(keys(var.chains),count.index),"0")}"
+
 
   depends_on = ["aws_security_group.database"]
 
diff --git a/roles/main_infra/files/variables.tf b/roles/main_infra/files/variables.tf
index 7c83e32..2ead479 100644
--- a/roles/main_infra/files/variables.tf
+++ b/roles/main_infra/files/variables.tf
@@ -8,6 +8,7 @@ variable "dns_zone_name" {}
 variable "instance_type" {}
 variable "root_block_size" {}
 variable "pool_size" {}
+variable "elixir_version" {}
 
 variable "key_content" {
   default = ""
@@ -71,6 +72,10 @@ variable "chain_db_storage_type" {
   default = {}
 }
 
+variable "chain_db_iops" {
+  default = {}
+}
+
 variable "chain_db_instance_class" {
   default = {}
 }
diff --git a/roles/main_infra/templates/terraform.tfvars.j2 b/roles/main_infra/templates/terraform.tfvars.j2
index f00a9f2..6d405e1 100644
--- a/roles/main_infra/templates/terraform.tfvars.j2
+++ b/roles/main_infra/templates/terraform.tfvars.j2
@@ -16,6 +16,7 @@ use_ssl               = "{{ use_ssl }}"
 new_relic_app_name    = "{{ new_relic_app_name }}"
 new_relic_license_key = "{{ new_relic_license_key }}"
 secret_key_base       = "{{ secret_key_base }}" 
+elixir_version        = "{{ elixir_version }}"
 
 chains = {
 {% for key, value in chains.iteritems() %}
@@ -149,6 +150,12 @@ chain_db_storage_type = {
 {% endfor %}
 }
 
+chain_db_iops = {
+{% for key, value in chain_db_iops.iteritems() %}
+{{ key }} = "{{ value }}"{% if not loop.last %},{% endif %}
+{% endfor %}
+}
+
 chain_db_version = {
 {% for key, value in chain_db_version.iteritems() %}
 {{ key }} = "{{ value }}"{% if not loop.last %},{% endif %}