DynamoDB Accelerator (DAX) Exam Tips

DynamoDB Accelerator (DAX) is a fully managed, clustered in-memory cache for DynamoDB. Only for Reads

Delivers up to a 10x read performance improvement
Microsecond performance for millions of requests per second
Idead for read-heavy and bursty workflows
E.g. auction applications, gaming, and retail sites during Black Friday promotions

How does it work

DAX is a write-through caching service - this means data is written to the cache as well as back end store at the same time
Allows you to point your DynamoDB API calls at the DAX cluster
If the item you are querying is in the cache (cache hit), DAX returns the result to the application.
If the item is not available (cache miss) then DAX performs an Eventually Consistent GetItem operation against DynamoDB
Retrieval of data from DAX reduces the read load on DynamoDB tables
May be able to reduce Provisioned Read Capacity

Caters for Eventually Consisten reads only - so not suitable for applications that require Strongly Consistent reads
Write intensive applications
Applications that do not perform many read operations
Applications that do not require microsecond response times. You shouldn't use DAX if you don't need that microsecond low-latency