DynamoDB 推出的新架構，在系統上幫忙處理 cache：「Amazon DynamoDB Accelerator (DAX) – In-Memory Caching for Read-Intensive Workloads」。
DAX 跟現有的 DynamoDB API 相容：
DAX is a fully managed caching service that sits (logically) in front of your DynamoDB tables. It operates in write-through mode, and is API-compatible with DynamoDB.
因為 cache 的緣故，會是 eventually-consistent 架構：
Responses are returned from the cache in microseconds, making DAX a great fit for eventually-consistent read-intensive workloads.
然後是 r3 系列的機器組成的，限制在十台 (冒出大大的問號)：
Each DAX cluster can contain 1 to 10 nodes; you can add nodes in order to increase overall read throughput. The cache size (also known as the working set) is based on the node size (dax.r3.large to dax.r3.8xlarge) that you choose when you create the cluster. Clusters run within a VPC, with nodes spread across Availability Zones.
不是很清楚這樣的好處 (比起自己用 memcached 或是其他類似的 cache 架構)，也許過幾天想通了會開竅... :o