AWS 推出了 CloudWatch Metric Streams，把 CloudWatch Metric 的資料往 Kinesis Data Firehose 裡面丟：「CloudWatch Metric Streams – Send AWS Metrics to Partners and to Your Apps in Real Time」。

其中一個賣點是即時性比用 API 去拉好很多：

In order to make it easier for AWS Partners and others to gain access to CloudWatch metrics faster and at scale, we are launching CloudWatch Metric Streams. Instead of polling (which can result in 5 to 10 minutes of latency), metrics are delivered to a Kinesis Data Firehose stream.

格式上可以是 JSON 或是 Open Telemetry：

When you set up a stream you choose between the binary Open Telemetry 0.7 format, and the human-readable JSON format.

另外一個賣點是價位，每千次 $0.003：

Pricing – You pay $0.003 for every 1000 metric updates, and for any charges associated with the Kinesis Data Firehose. To learn more, check out the pricing page.

另外算一下 Kinesis Data Firehose 的價錢，是以資料量的大小計費，不過最小計價單位是 5KB (一筆應該是不會到)，單價是 $0.029/GB (us-east-1) 或是 $0.037/GB (ap-southeast-1)，算了一下跟 CloudWatch Metrics Streams 比起來只是零頭...

之前如果要自己拉出來的話是透過 API call 抓，每 1000 次是 USD$0.01，這個方法相較起來便宜不少，不過數量多的時候還是一筆費用 (而且有不少 metrics 是一分鐘更新一次)。

如果只是要備份起來或是跑分析的話，也許先前用 API 拉的作法可能還是比較好？一個小時拉一次對於備份與分析應該都很夠了，而 alarm 的機制還是掛在 CloudWatch 上。

這次產品的定位看起來是要把 ecosystem 做起來：

We designed this feature with the goal of making it easier & more efficient for AWS Partners including Datadog, Dynatrace, New Relic, Splunk, and Sumo Logic to get access to metrics so that the partners can build even better tools.