Event filter based on previous event

Question

I want to trigger a Lambda function in an event driven way.

My final goal is to aggregate a timeseries table that is getting data from a IoT Thing.
The IoT data is going directly to a DynamoDB table, and I want to resample this 10 secondly data to a 5 minutes data in another DynamoDB table.

My idea is to somehow compare the latest added item with the previous item, and if it crossed the 00 or 05 minute mark, trigger the lambda function.
I want to save lambda executions so is there a way of achieving this in the event filtering?

EDIT: Something that would also help - test if the timestamp value minute is a multiple of 5. I would still have unnecessary activations but way less.

Answer

You don't need to use eventFiltering, you can achive that using Lambda [`BatchWindow`](https://aws.amazon.com/about-aws/whats-new/2019/09/aws-lambda-now-supports-custom-batch-window-for-kinesis-and-dynamodb-event-sources/). This will invoke your function when the payload size reaches 6MB, the Batch Window reaches its maximum value, or the Batch Size reaches its maximum value. So its important to ensure your `BatchSize` is large enough to let it wait for the window to trigger.

Answer

Unfortunately, there is no way to do that. You will need to invoke your function for every event and check if you actually need to do something or not, based on some state that you will save somewhere.

Event filter based on previous event

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