UUIDs for DynamoDB?

Question

Is it possible to get DynamoDB to automatically generate unique IDs when adding new items to a table?

I noticed the Java API mentions @DynamoDBAutoGeneratedKey so I\

Answer 1

The approach I'm taking is to use the current timestamp for the hash-key (or the range-key, if using a range-key too). Store the timestamp as an integer, representing the number of milliseconds since the start of the "UNIX epoch" (in the UTC timezone). Many date/time libraries can produce this number for you.

This has the advantage that if you want to have a "creation time" field in your table, your UUID already stores this information. Just call another method in your date/time library to convert the timestamp to a readable format.

(Be sure to handle the exception which will occur if a second item is created in the same table with the same millisecond timestamp; just fall back and retry the operation in that case, with a slightly later, current timestamp.)

For example:

User table

hash-key only: userID (timestamp of the creation of this user).

WidgetAttributes table

hash-key plus range-key.
hash-key: userID (use the userID from the User table of the user to whom the widget belongs). range-key: attribID (use the timestamp of the creation of this widget-attribute).

Now you can run "query" operations on the WidgetAttributes table to get all widget-attributes for a certain user; by using "greater-than-zero" as the query-parameter for the range-key.