AWS customers are making great use of Amazon DynamoDB. They love the speed and flexibility and build Ad Tech (reference architecture), Gaming (reference architecture), IoT (reference architecture), and other applications that take advantage of the consistent, single-digit millisecond latency. They also love the fact that DynamoDB is a managed, serverless database that scales to handle millions of requests per second to tables that are many terabytes in size.
Many DynamoDB users store data that has a limited useful life or is accessed less frequently over time. Some of them track recent logins, trial subscriptions, or application metrics. Others store data that is subject to regulatory or contractual limitations on how long it can be stored. Until now, these customers implemented their own time-based data management. At scale, this sometimes meant that they ran a couple of Amazon Elastic Compute Cloud (EC2) instances that did nothing more than scan DynamoDB items, check date attributes, and issue delete requests for items that were no longer needed. This added cost and complexity to their application.
New Time to Live (TTL) Management
In order to streamline this popular and important use case, we are launching a new Time to Live (TTL) feature today. You can enable this feature on a table-by-table basis, specifying an item attribute that contains the expiration time for the item.
Once the attribute has been specified and TTL management has been enabled (a single API call takes care of both operations), DynamoDB will find and delete items that have expired. This processing takes place automatically and in the background and does not affect read or write traffic to the table.
You can use DynamoDB streams (see Sneak Preview – DynamoDB Streams for more info) to process or archive the actual deletions. Like other update records in a stream, the deletions are available on a rolling 24-hour basis. You can move the expired items to cold storage, log them, or update other tables using AWS Lambda and DynamoDB Triggers.
Here’s how you enable TTL for a table and specify the desired attribute:
The attribute must be in DynamoDB’s Number data type, and is interpreted as seconds per the Unix Epoch time system.
As you can see from the screen shot above, you can also enable DynamoDB Streams, and you can look at a preview of the items that will be deleted when you enable TTL.
You can also call the
UpdateTimeToLive function from your code, or you can use the
update-time-to-live command from the AWS Command Line Interface (CLI).