---
title: ElastiCache nodes not created across multi-AZ
description: Datadog, the leading service for cloud-scale monitoring.
breadcrumbs: >-
  Docs > Datadog Security > Code Security > Infrastructure as Code (IaC)
  Security > IaC Security Rules > ElastiCache nodes not created across multi-AZ
---

# ElastiCache nodes not created across multi-AZ

{% callout %}
# Important note for users on the following Datadog sites: app.ddog-gov.com, us2.ddog-gov.com

{% alert level="danger" %}
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{% /callout %}

## Metadata{% #metadata %}

**Id:** `cloudformation-aws-elasticache-nodes-not-created-across-multi-az` 

**Provider:** AWS

**Platform:** CloudFormation

**Severity:** Medium

**Category:** Availability

#### Learn More{% #learn-more %}

- [Provider Reference](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-properties-elasticache-cache-cluster.html)

### Description{% #description %}

Multi-node Amazon ElastiCache (Memcached) clusters must be deployed across multiple Availability Zones to maintain availability and avoid complete cluster outage if a single Availability Zone fails.

The `AZMode` property on `AWS::ElastiCache::CacheCluster` must be set to `cross-az` for resources with `Engine` set to `memcached` and `NumCacheNodes` greater than `1`. If `AZMode` is omitted, the cluster defaults to `single-az`, so resources missing `AZMode` or with `AZMode` not equal to `cross-az` will be flagged as a configuration risk.

Secure configuration example:

```yaml
MyCacheCluster:
  Type: AWS::ElastiCache::CacheCluster
  Properties:
    Engine: memcached
    NumCacheNodes: 3
    AZMode: cross-az
    CacheNodeType: cache.m6g.large
```

## Compliant Code Examples{% #compliant-code-examples %}

```yaml
AWSTemplateFormatVersion: "2010-09-09"
Resources:
  myCacheCluster:
    Type: 'AWS::ElastiCache::CacheCluster'
    Properties:
      AZMode: cross-az
      CacheNodeType: cache.m3.medium
      Engine: memcached
      NumCacheNodes: '3'
      PreferredAvailabilityZones:
        - us-west-2a
        - us-west-2a
        - us-west-2b
```

```json
{
  "Resources": {
    "myCacheCluster2": {
      "Type": "AWS::ElastiCache::CacheCluster",
      "Properties": {
        "AZMode": "cross-az",
        "CacheNodeType": "cache.m3.medium",
        "Engine": "memcached",
        "NumCacheNodes": "3",
        "PreferredAvailabilityZones": [
          "us-west-2a",
          "us-west-2a",
          "us-west-2b"
        ]
      }
    }
  }
}
```

## Non-Compliant Code Examples{% #non-compliant-code-examples %}

```yaml
AWSTemplateFormatVersion: "2010-09-09"
Resources:
  myCacheCluster3:
    Type: 'AWS::ElastiCache::CacheCluster'
    Properties:
      AZMode: single-az
      CacheNodeType: cache.m3.medium
      Engine: memcached
      NumCacheNodes: '3'
      PreferredAvailabilityZones:
        - us-west-2a
        - us-west-2a
        - us-west-2b
```

```yaml
AWSTemplateFormatVersion: "2010-09-09"
Resources:
  myCacheCluster4:
    Type: 'AWS::ElastiCache::CacheCluster'
    Properties:
      CacheNodeType: cache.m3.medium
      Engine: memcached
      NumCacheNodes: '3'
      PreferredAvailabilityZones:
        - us-west-2a
        - us-west-2a
        - us-west-2b
```

```json
{
  "Resources": {
    "myCacheCluster5": {
      "Type": "AWS::ElastiCache::CacheCluster",
      "Properties": {
        "AZMode": "single-az",
        "CacheNodeType": "cache.m3.medium",
        "Engine": "memcached",
        "NumCacheNodes": "3",
        "PreferredAvailabilityZones": [
          "us-west-2a",
          "us-west-2a",
          "us-west-2b"
        ]
      }
    }
  }
}
```