DynamoDB Accelerator (DAX)

• Fully managed, highly scalable, seamless in-memory cache for DynamoDB.

• Not part of free-tier.

• Port is 8111 for non-encrypted access and 9111 if encrypted in transit.

• Microseconds latency for cached reads and queries.

• Does not require application logic modification (compatible with DynamoDB APIs).

• It solves the hotkey problem.

  • If a particular key are read frequently and data is not modified often, then DAX can alleviate the RCU throttling as result could be cached at DAX cluster.

• Secured with support for encryption at rest with KMS, VPC security, IAM, CloudTrail integration etc.

• TTL can be configured at cluster level using parameter group

  • By default an item can be cached for upto 5 minutes

  • By default a query can be cached for upto 5 minutes

• Typically an application should use cluster endpoint.

Node Families

Node Type	Description
t-type	Used when requires lower throughput.
r-type	Always ready capacity.

• Upto 10 nodes can be present in cluster.

• Recommended to have atleast 3 nodes minimum in a multi-AZ setup for High Availability (HA) in production .

• There are different node types which is categorized based on capacity.

Why to use DynamoDB DAX when ElastiCache is present

• DAX is typically used to cache simple types of query result like objects, individual query result or table scan result.

• ElasticCache is typically used seldom changing result but are computationally expensive or network overheads or aggregrate result.

Diagram

DAX Cluster

References

• DAX