Amazon DynamoDB - geographically distributed?

Question

I am new to AWS. Sorry if my question is basic, got stuck with this term.

AWS Global Infrastructure says "18 geographic Regions" -> Geographic term is used along with Regions, that makes sense.

DynamoDB FAQs 3rd questions says, "Amazon DynamoDB stores three geographically distributed replicas of each table to enable high availability and data durability."

Here(three geographically) is it referring to Region or Availability Zones ? Bit confused. If it is Region, does it mean my data is going out of my country(if my country has only 1 Region).

Please suggest.

Answer 1

Almost every AWS service revolves around two things in availability: Multi AZ (multiple data centers in a single region) and Cross-Region (different geographic locations across globe) and so does the DynamoDB. By default AWS DynamoDB is a multi-AZ enabled service which means that your data is by default replicated across 3 data centers (minimum of 2 AZs) but for cross-region, you need to enable DynamoDB global tables (DynamoDB Streams).

Answer 2

Multi-Region Replication with DynamoDB

DynamoDB global tables are geographically distributed. They provide a fully managed solution for deploying a multiregion, multi-active database. Like with every other geographically distributed database, GlobalTables comes with ReplicationLatency.

An important thing to note here is, DynamoDB does not offer cross-region strong consistency (this is in contrast with CosmosDB, a similar offering from Azure)

From AWS documentation:

An application can read and write data to any replica table. If your application only uses eventually consistent reads and only issues reads against one AWS Region, it will work without any modification. However, if your application requires strongly consistent reads, it must perform all of its strongly consistent reads and writes in the same Region. DynamoDB does not support strongly consistent reads across Regions. Therefore, if you write to one Region and read from another Region, the read response might include stale data that doesn't reflect the results of recently completed writes in the other Region.

Also, global tables are not to be confused with global indexes. Global indexes get their name because they are used in fetching data across multiple DynamoDB partitions.

Answer 3

"Amazon DynamoDB stores three geographically distributed replicas of each table to enable high availability and data durability."

This is specifically referring to multi AZ structure of dynamo, this helps in achieving high availability of your table. eg. if one of availability zone is down you still will be able to access you table.

To answer "my data is going out of my country(if my country has only 1 Region)."

For multi region its not by default ON you need to use global tables and specify regions in which you want to replicate that means your data/table wont go in any other region till you specifically want it to be.

For more on global tables refer https://aws.amazon.com/dynamodb/global-tables/