[nadieyninguno1]

> * Very very low traffic apps. POST hooks for Slack bots, etc.. Works well!

I would add, that it offers an extension point / hook-in for a variety of AWS products. I can add custom functions to be called when a Cognito user is created, updated. I can add custom functions to be called to authorize routes transiting API Gateway.

At "The Firm" - we're going heavily in on AWS for our architecture - Fargate for k8s on top of the usual RDS, S3, etc.

We've begun roll-out of an external-facing API authenticated with OAuth2. Our backing store here is Cognito and our routing happens via API Gateway. We use the API Gateway's baked-in Cognito token authorizer for incoming requests, which route to pods hosted in Fargate. These pods represent a variety of projects.

As such we have two Lambda functions providing the /oauth/secret and /oauth/token endpoints for exchange of One-Time-Password for a secret token and secret token for access tokens - they experience very low N call rates (dozens?) of times per day and don't fit into any given API we host via Fargate.

[minimaul]

We use Lambda to handle lots of scale-out tasks & extensions to AWS services too - it works really well for this.

For example:

- resizing images - we can do a size per lambda all in parallel. This means we can process images quickly (with minimal latency) without having to have loads of slack memory & CPU on our backends

- queue processing - we have an app that needs to copy files from user provided URLs to S3. We do this by dumping them in a SQS queue and having a lambda fire for each queue item. Means we can do lots in parallel without filling up an EC2/fargate instance’s network port

- dynamically processing images using Lambda@Edge & Cloudfront - similar to my first one, but on the fly when requested, instead of ahead of time

[ovao]

To add a couple more good use cases for Lambda:

- To run something at deploy-time with custom CloudFormation resources. As an example, a Lambda can be invoked during each deployment to run tests. If the test fails, the stack(s) can be automatically rolled back. Tricky to get right and not often the right tool in the bag, but sometimes useful.

- As handlers for CloudWatch events. Useful for forwarding events to third-party log services, or for taking some sort of complex action based on a given event.

AWS is nearly “all in” on Lambda at this point, so it’s a good bet that if you want to hang some kind of task off an AWS service, they’ll give you a hook to fire off a Lambda. From a cost and simplicity perspective this works out well.