You can use SNS FIFO topics in all commercial regions. You can process up to 300 transactions per second (TPS) per FIFO topic or FIFO queue. With SNS, you pay only for what you use, you can find more information in the pricing page.
Pricing for continuous backups is detailed on the DynamoDB Pricing Pages. Pricing varies by region and is based on the current size of the table and indexes. For example, in US East (N. Virginia) you pay $0.20 per GB based on the size of the data and all local secondary indexes.
有這樣的功能通常是一開始設計時就有考慮 (讓底層的資料結構可以很方便的達成這樣的效果)，現在只是把功能實作出來... 像 MySQL 之類的軟體就沒辦法弄成這樣 XDDD
最後有提到支援的地區，是用條列的而不是說所有有 Amazon DynamoDB 的區域都支援：
PITR is available in the US East (N. Virginia), US East (Ohio), US West (N. California), US West (Oregon), Asia Pacific (Tokyo), Asia Pacific (Seoul), Asia Pacific (Mumbai), Asia Pacific (Singapore), Asia Pacific (Sydney), Canada (Central), EU (Frankfurt), EU (Ireland), EU (London), and South America (Sao Paulo) Regions starting today.
For example, in early 2016 Facebook spent roughly 7% of its total JavaScript time during startup in the implementation of for-in itself. On Wikipedia this number was even higher at around 8%.
可以看得出來是挑比較大的來改，而下一版的 Google Chrome (57) 將會對 for-in 會到另外一個極致：
The most important for-in helpers are at position 5 and 17, accounting for an average of 0.7% percent of the total time spent in scripting on a website. In Chrome 57 ForInEnumerate has dropped to 0.2% of the total time and ForInFilter is below the measuring threshold due to a fast path written in assembler.
主要是因為 spec 對 for-in 的定義寫得很模糊，所以就有很多實作的空間可以調整：
When we look at the spec-text of for-in, it’s written in an unexpectedly fuzzy way,which is observable across different implementations.
In addition to having all the capabilities of the standard queue, FIFO (First-In-First-Out) queues are designed to enhance messaging between applications when the order of operations and events is critical, or where duplicates can't be tolerated. FIFO queues also provide exactly-once processing but are limited to 300 transactions per second (TPS).
Q: Does Amazon SQS provide first-in-first-out (FIFO) access to messages?
Amazon SQS provides a loose-FIFO capability that attempts to preserve the order of messages. However, we have designed Amazon SQS to be massively scalable using a distributed architecture. Thus, we can't guarantee that you will always receive messages in the exact order you sent them (FIFO).
If your system requires the order of messages to be preserved, place sequencing information in each message so that messages can be ordered when they are received.
而現在則是名正言順的說有提供 FIFO 了：
Q: Does Amazon SQS provide message ordering?
Yes. FIFO (first-in-first-out) queues preserve the exact order in which messages are sent and received. If you use a FIFO queue, you don't have to place sequencing information in your messages. For more information, see FIFO Queue Logic in the Amazon SQS Developer Guide.
Standard queues provide a loose-FIFO capability that attempts to preserve the order of messages. However, because standard queues are designed to be massively scalable using a highly distributed architecture, receiving messages in the exact order they are sent is not guaranteed.
