Lambda triggers and event source mappings

Lambda triggers are especially useful for kicking off numerous applications when a piece of data is uploaded to a specific S3 bucket. AWS provides examples of images being uploaded to buckets in many of its talks and presentations. This image then triggers a Lambda function, which will resize the image so that it's more compressed and then place it in a folder for GIFs. Many times, this same function will place a pointer for the newly resized image in a DynamoDB table. These resized images are more accessible and quicker for end users to download, and this all happens automatically once a source image has been uploaded:

Figure 12.5 – The flow of an image being uploaded to an S3 bucket that triggers a Lambda function for image resizing

There are even more things we can do with bucket triggers than just image resizing, especially in an enterprise and DevOps context. Remember that S3 can be used as source...