Terraform AWS ElastiCache Module Deep Dive

Infrastructure as code for AWS ElastiCache has become a critical capability for teams that need predictable, repeatable deployment of managed Redis and Memcached services. The Terraform AWS ElastiCache module provides a consistent interface for creating various ElastiCache deployment types while handling the underlying complexity of resource configurations, security settings, parameter groups, and networking requirements.

The module is designed to simplify the provisioning and management of AWS ElastiCache resources through Terraform. It supports multiple deployment types including Memcached clusters, Redis/Valkey clusters, replication groups, and serverless cache deployments. Amazon ElastiCache gives you managed Redis or Memcached clusters, handling the infrastructure, patching, and failover so you can focus on your application.

Overview

The terraform-aws-elasticache module enables infrastructure-as-code creation and management of AWS ElastiCache resources. It provides a consistent interface for creating various ElastiCache deployment types while handling the underlying complexity of resource configurations, security settings, parameter groups, and networking requirements.

The module is built to streamline operations, automate workflows, enhance collaboration and, most importantly, deploy with confidence. It is maintained with a focus on Automation and the belief in splitting infrastructure into smaller connected resources which could be standardized, are manageable, scalable, secure and follow industry best practices.

The module includes Terraform open source, examples, and automation tests which would help you create and improve your infrastructure with minimalistic coding.

Core Components

The AWS ElastiCache Terraform module consists of several integrated components that work together to create and manage ElastiCache resources.

The module can create standalone ElastiCache clusters, primarily used for Memcached deployments or single-node Redis deployments.

aws_elasticache_cluster

Key configuration options for this component are used for standalone cluster creation.

For Redis/Valkey deployments requiring high availability or read scaling, the module creates replication groups with primary and replica nodes.

aws_elasticache_replication_group

Key configuration options for replication groups support high availability configurations.

For multi-region Redis deployments, the module supports creating global replication groups.

aws_elasticache_global_replication_group

This allows multi-region replication patterns.

aws_elasticache_parameter_group

Customizes the behavior of the ElastiCache engine through configurable parameters.

aws_elasticache_subnet_group

Specifies the VPC subnets where ElastiCache nodes are deployed.

aws_security_group
aws_vpc_security_group_ingress_rule
aws_vpc_security_group_egress_rule

Manages network access to ElastiCache resources.

aws_cloudwatch_log_group

Configures log delivery for ElastiCache operations, particularly for Redis slow logs.

The following table summarizes the core resources managed by the module.

Deployment Patterns

Here are example configurations for common ElastiCache deployment patterns.

Used for caching with no data persistence requirements and horizontal scaling.

Used for high availability and data persistence with primary and replica nodes.

Used for sharded Redis deployments for increased data capacity.

The module supports deployment types for Memcached clusters, Redis/Valkey clusters, replication groups, and serverless cache deployments.

Simple Redis Cluster

For development or simple caching needs, a single-node Redis cluster works fine.

Example configuration for a single-node Redis cluster:

hcl resource "aws_elasticache_cluster" "redis_dev" { cluster_id = "myapp-cache-dev" engine = "redis" engine_version = }

Memcached Cluster Example

A working example for a Memcached deployment with cross AZ mode:

```hcl
module "elasticache" {
source = "terraform-aws-modules/elasticache/aws"
clusterid = "example-memcached"
createcluster = true
createreplicationgroup = false
engine = "memcached"
engineversion = "1.6.17"
nodetype = "cache.t4g.small"
numcachenodes = 2
azmode = "cross-az"
maintenancewindow = "sun:05:00-sun:09:00"
apply_immediately = true

vpcid = module.vpc.vpcid
securitygrouprules = {
ingressvpc = {
description = "VPC traffic"
cidripv4 = module.vpc.vpccidrblock
}
}

subnetids = module.vpc.privatesubnets

createparametergroup = true
parametergroupfamily = "memcached1.6"
parameters = [
{
name = "idle_timeout"
value = 60
}
]

tags = {
Terraform = "true"
Environment = "dev"
}
}
```

Redis Example

Redis deployment example with maintenance window and apply immediately:

```hcl
module "elasticache" {
source = "terraform-aws-modules/elasticache/aws"
clusterid = "example-redis"
createcluster = true
createreplicationgroup = false
engineversion = "7.1"
nodetype = "cache.t4g.small"
maintenancewindow = "sun:05:00-sun:09:00"
applyimmediately = true

vpcid = module.vpc.vpcid
securitygrouprules = {
ingressvpc = {
description = "VPC traffic"
cidripv4 = module.vpc.vpccidrblock
}
}

subnet_ids =
}
```

Networking and Security Prerequisites

ElastiCache runs in your VPC and needs a subnet group and security group.

Subnet group for ElastiCache:

hcl resource "aws_elasticache_subnet_group" "main" { name = "cache-subnet-group" subnet_ids = var.private_subnet_ids tags = { ManagedBy = "terraform" } }

Security group for ElastiCache:

hcl resource "aws_security_group" "cache" { name_prefix = "cache-" vpc_id = var.vpc_id description = "Security group for ElastiCache" ingress { from_port = 6379 to_port = 6379 protocol = "tcp" security_groups = [var.app_security_group_id] description = "Redis from application" } ingress { from_port = 11211 to_port = 11211 protocol = "tcp" security_groups = [var.app_security_group_id] description = "Memcached from application" } egress { from_port = 0 to_port = 0 protocol = "-1" cidr_blocks = ["0.0.0.0/0"] } lifecycle { create_before_destroy = true } }

The module manages network access through awssecuritygroup, awsvpcsecuritygroupingressrule and awsvpcsecuritygroupegressrule.

A security group to control network access to Redis cluster can be defined as:

hcl resource "aws_security_group" "redis_sg" { name = "redis-security-group" description = "Security group for Redis cluster" ingress { from_port = 6379 to_port = 6379 protocol = "tcp" cidr_blocks = ["0.0.0.0/0"] } }

Provider Requirements and Prerequisites

Before you start, ensure you have the following:

• AWS Account: An active AWS account with the necessary permissions.
• Terraform Installed: Terraform should be installed and configured on your local machine.
• AWS Access Key and Secret Key: You'll need these to authenticate Terraform with AWS.

Start by defining the AWS provider:

hcl provider "aws" { region = "ap-southeast-2" access_key = "your-access-key" secret_key = "your-secret-key" }

Prerequisites and providers for the community module:

Module requirements:

IMPORTANT: Since the master branch used in source varies based on new modifications, we recommend using the release versions.

The module has dependencies which should be referenced for complete usage.

Configuration Options

Key configuration options for standalone clusters include cluster ID, engine, engine version, node type, num cache nodes, az mode, maintenance window, apply immediately.

Key configuration options for replication groups include primary and replica node settings, high availability configuration.

Parameter group customization allows engine behavior tuning via configurable parameters.

Subnet group specifies the VPC subnets where ElastiCache nodes are deployed.

Security group rules can be defined with ingress VPC traffic, default port based on engine, description and cidr_ipv4.

Parameter group family can be set for Memcached, with parameters such as idle_timeout value 60.

Tags can be applied for Terraform management and environment identification.

Best Practices and Production Considerations

In this post, we'll set up ElastiCache clusters with Terraform, covering both Redis which is far more popular and Memcached, along with production configurations for encryption, replication, and automatic failover.

Networking prerequisites remain essential for production deployments. ElastiCache runs in your VPC and needs a subnet group and security group.

For production, restrict security group cidr_blocks to specific IPs for better security rather than 0.0.0.0/0.

Use maintenance_window settings such as sun:05:00-sun:09:00 to control updates.

Apply immediately can be set to true for non-production environments, with caution in production.

Create parameter group with appropriate parametergroupfamily for the engine version.

Use cross-AZ mode for Memcached clusters to improve availability.

Use replication groups for high availability and data persistence with primary and replica nodes.

Conclusion

The AWS ElastiCache Terraform module provides a comprehensive and technically dense approach to provisioning ElastiCache resources through infrastructure as code. It covers standalone clusters for Memcached and single-node Redis, replication groups for high availability Redis/Valkey, global replication groups for multi-region deployments, parameter groups for engine tuning, subnet groups for VPC placement, security groups for network access, and CloudWatch log groups for operational visibility.

The module offers consistent interfaces across deployment patterns while abstracting the underlying complexity of AWS resource configurations, security settings, parameter groups, and networking requirements. With defined prerequisites for Terraform, AWS provider, and Random provider versions, and with extensive example deployments for caching without persistence, high availability with persistence, and sharded Redis for increased capacity, it serves as a repeatable foundation for both development and production ElastiCache workloads.

Adopting the module reduces manual configuration drift, enforces security best practices through declarative security group and subnet definitions, and enables teams to focus on application logic rather than infrastructure maintenance. When combined with proper networking prerequisites, parameter customization, and tagging strategies, the module delivers a scalable and secure ElastiCache foundation managed entirely through Terraform.

Sources

1. deepwiki.com/terraform-aws-modules/terraform-aws-elasticache
2. github.com/clouddrove/terraform-aws-elasticache
3. oneuptime.com/blog/post/2026-02-12-create-elasticache-clusters-with-terraform/view
4. github.com/terraform-aws-modules/terraform-aws-elasticache
5. dev.to/giasuddin90/creating-an-aws-elasticache-redis-cluster-using-terraform-eb6