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

Geographically isolated in this documentation refers to Availability Zones and not Regions. As per AWS documentation when you create a table in one region, it's replicated in others zones to ensure the high availability. If you do some activity in the table it's updated in the replicas. The AZ's are interconnected with low latency networks.

The data is stored on SSD disks and automatically replicated across multiple Availability Zones in an AWS region, which brings the high availability and your data is durable.

If you create a table in one region, the same table can be created in other regions also with same name.

If you want your table to be replicated in other regions you must enable the Cross-Region replication. For more details Refer

DynamoDB

All Things about DynamoDB

Answer 2

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 3

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.