DynamoDB

Para can work with DynamoDB by using the DynamoDB DAO plugin which provides the AWSDynamoDAO implementation. That class is responsible for connecting to Amazon’s DynamoDB server and storing/retrieving objects (items) to/from it. All operations are carried out using the latest AWS Java SDK.

Batch updates

DynamoDB doesn’t support batch update requests so AWSDynamoDAO does not batch update requests. It simply executes all update requests in a sequence.

The implementation adds a default prefix para- to DynamoDB tables, so if you have an app called “myapp” your table for that will be called para-myapp.

This DAO implementation supports optimistic locking through conditional update expressions in DynamoDB.

Server-side encryption (SSE, encryption-at-rest) is enabled by default for all tables. To switch between from AWS-owned CMK to using your account’s KMS, the following property:

para-application.conf

para.dynamodb.sse_enabled = true

When this is true, your account’s KMS will be used for encrypting the data in the table, otherwise an AWS-owned CMK will be used. Defaults to false.

Encryption at rest

SSE will work for newly created tables only. Currently, you can’t enable encryption at rest on an existing table. After encryption at rest is enabled, it can’t be disabled.

Table sharing

In v1.21, we added new functionality to AWSDynamoDAO which enables apps to share the same table. This is useful for certain deployment scenarios where you have a large number of apps (and tables) which are rarely accessed and have low throughput. This makes it expensive to run Para on many DynamoDB tables which remain underutilized for long periods of time. So with table sharing you can reduce your DynamoDB bill to a minimum by having a shared table that contains all the objects for all those apps. You can enable this feature by setting the following in your config:

para-application.conf

para.prepend_shared_appids_with_space = true

This will prepend the appid property with a space character for those apps that have isSharingTable set to true, thus letting the DAO know that this app belongs to the shared table, instead of sending its data to a separate table. The shared table name is controlled by para.shared_table_name and defaults to “0”.

The shared table keys are a combination of appid and id (e.g. myapp_679334060962615296). Para will also automatically create a global secondary index (GSI) on the shared table, with a primary key appid and secondary key timestamp, to facilitate queries like dao.readPage().

See Modules for more information about how you can override the default implementation.

AWS documentation

For more information about DyanamoDB see the documentation on AWS.