Can I trigger a Lambda function or SNS event in response to an AppSync GraphQL Mutation?

[scherroman]

Which Category is your question related to?

Usage Question

What AWS Services are you utilizing?

Amplify, AppSync, Lambda, SNS, DynamoDB

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AWS AppSync/GraphQL subscriptions coupled with AWS Amplify sound amazing, since out of the box you can subscribe all your clients to high-level domain events specified in your schema.

Though it seems like a natural extension that there should be a way to broadcast all those events to a service like lambda or SNS to react internally to those events. Maybe you want to log the events, re-index or aggregate updated data, or send an email or push notification to a user. Just like DynamoDB Streams allows you to trigger a lambda upon to updates on a table. Is anyone aware of a good way to achieve this?

There appears to be no AppSync trigger source for lambda, but it seems like there might be a couple of ways to do this otherwise:

1. Create a long-running process/service on ECS/Fargate that subscribes to every mutation it wants to broadcast to SNS/Lambda. Though you would have to manage and scale that process yourself 😬

2. Use DynamoDB Streams as a lambda trigger. However, a DynamoDB table change event is lower-level than a GraphQL mutation event, and this assumes your only data source is DynamoDB, whereas AppSync/GraphQL can plug into many other data sources.

3. Create lambda resolvers for every mutation that also broadcast the event to SNS/Lambda. For simply broadcasting SNS events, perhaps theres a clever way to use pipeline resolvers to attach a reusable resolver to every mutation...

I'm not sure how the Amplify framework powers their @searchable transformer, whether its the 2nd or 3rd method, or something else altogether, but it seems like that's in the same ballpark (re-indexing the data in Elasticsearch in response to an update). I do remember hearing you can write your own transformers ... perhaps one could write their own transformer @broadcasted that also broadcasts all mutation events to SNS 🤔

I'm surprised I haven't seen much if any discussion surrounding this topic. If anyone has some ideas or if I'm thinking about this the wrong way let me know!

[scherroman]

Closing as I think is more appropriate to ask on the amplify-cli project where the GraphQL Transformer exists today.

Opened a question issue here

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