What event can be triggered to fire a lambda function in DynamoDB?

Question

I can't seem to find the documentation on what kinds of events DynamoDB is able to trigger a lambda function based on. All I can find is mentions of when a new record is added to a table or a record is updated. Are those the two "only" actions/events available? Or could I also trigger a lambda function when I request a records that does not exists (which is what I need in my case, where I will be using DynamoDB as a cache)?

Answer 1

Triggering AWS Lambda through events happening in DynamoDB is done by utilizing DynamoDB Streams.

As stated in the documentation:

DynamoDB Streams captures a time-ordered sequence of item-level modifications in any DynamoDB table, and stores this information in a log for up to 24 hours.

So they only capture operations which modify data, which isn't the case for read operations.

Answer 2

Triggering a Lambda function automatically because somebody queried for a key that doesn't exist is not supported by DynamoDB. You would have to handle that in your querying code.