Best practices and requirements for managing global tables - Amazon DynamoDB
Services or capabilities described in Amazon Web Services documentation might vary by Region. To see the differences applicable to the China Regions, see Getting Started with Amazon Web Services in China.

Best practices and requirements for managing global tables

There are two versions of DynamoDB global tables available: Version 2019.11.21 (Current) and Version 2017.11.29. To find out which version you are using, see Determining the version.

Using Amazon DynamoDB global tables, you can replicate your table data across Amazon Regions. It is important that the replica tables and secondary indexes in your global table have identical write capacity settings to ensure proper replication of data.

Warning

The table name for Global Tables must be unique within your Amazon acccount.

Requirements for Managing Capacity

A global table must have throughput capacity configured one of two ways:

  1. On-demand capacity mode, measured in replicated write request units (rWRUs)

  2. Provisioned capacity mode with auto scaling, measured in replicated write capacity units (rWCUs)

Using provisioned capacity mode with auto scaling or on-demand capacity mode helps ensure a global table has sufficient capacity to perform replicated writes to all regions of the global table.

Note

Switching from one table capacity mode to the other capacity mode in any Region switches the mode for all replicas.

Replicas and Calculating Write Units

For planning, you should take the number of writes that one Region will perform and add that to the number of writes happening for each other Region. This is critical as every write that is performed in one Region must also be performed in every replica Region. If you do not have enough capacity to handle all of the writes, capacity exceptions will occur. In addition, inter-regional replication wait times will rise.

For example, suppose that you expect 5 writes per second to your replica table in Ohio, 10 writes per second to your replica table in N. Virginia, and 5 writes per second to your replica table in Ireland. In this case, you should expect to consume 20 rWCUs or rWRUs in each Region: Ohio, N. Virginia, and Ireland. In other words, you should expect to consume 60 rWCUs total across all three Regions.

For details about provisioned capacity with auto scaling and DynamoDB, see Managing throughput capacity automatically with DynamoDB auto scaling.

Note

If a table is running in provisioned capacity mode with auto scaling, replicas in each Region may have different auto scaling configurations. It is best practice to set the same auto scaling policy in all Regions.