DynamoDB Accelerator (DAX)

Use in-memory caching to reduce read capacity costs for read-heavy workloads with high cache hit rates.

Overview

Amazon DynamoDB Accelerator (DAX) can help optimize costs for read-heavy workloads in DynamoDB. DAX is a fully managed, clustered in-memory cache that seamlessly integrates with DynamoDB, serving as a write-through caching layer for frequently accessed data.

Important: DAX is not serverless—it runs on provisioned EC2 instances, so it doesn’t come with all the benefits that exist in DynamoDB.

How DAX reduces costs

By caching frequently read data in memory, DAX reduces the read traffic to DynamoDB, resulting in cost savings. DynamoDB does not charge for read operations on cached items. However, as DAX incurs its own charges, you need to verify that the cost savings on DynamoDB outweigh the cost of DAX itself for your access pattern.

If using provisioned capacity mode, DAX can also lower the required provisioned read capacity.

When to use DAX

DAX is cost-effective when you have:

  • High read volume
  • High cache hit rate
  • Repeated reads of the same items

Monitoring

Track these CloudWatch metrics to ensure DAX is cost-effective:

  • Cache hit rate: Should be high for cost effectiveness
    • Formula: CacheHits / (CacheHits + CacheMisses) × 100%
  • ConsumedReadCapacityUnits: Monitor RCU reduction in DynamoDB
  • CPUUtilization: Right-size your cluster

Resources