AWS AppSync added support for Lambda authorizers on 30th July 2021 and it made it much easier to implement group-based authorization with 3rd party identity services. Group-based auth with AppSync and Cognito I previously wrote about how you can secure mu[...]

With API Gateway and Lambda, you can handle client errors gracefully by returning a 4xx response. module.exports.handler = async (event) => { // run validation logic return { statusCode: 400 } } This way, we can communicate clearly to the client that ther[...]

In the last post I discussed my preferred approach for modelling multi-tenant applications with AppSync and Cognito. This approach supports the common requirements in these applications, where there are a number of distinct roles within each tenant. This [...]

Thank you to Josh for asking this question on the AppSync Masterclass forum. His original question goes like this: Let’s say I want to add a one-to-many relationship from Profile to a new property called “Tag” (a complex object with “name” and “color” pro[...]

I have been involved with a client project to help the client launch a new social network for university students to engage with each other to do sports. Amongst other things, users can: Arrange activities and ask to join others’ activities (like a basket[...]

I previously wrote about five reasons you should consider AppSync over API Gateway. One thing that API Gateway supports but you can’t do with AppSync out-of-the-box yet is custom domain names. Your shiny new AppSync API is available at XYZ.appsync-api.us-[...]

I have been working with a US client to build a first-of-its-kind app for managing medical consents. It falls under HIPAA compliance and it’s paramount that we do not allow unauthorized access to user data. As part of the app, we have built an admin tool [...]

I have been working on a large AppSync project for a client these past few months. The initial version of the app was built in just a few weeks, but the client has commissioned additional features and the project has kept growing. At the time of writing, [...]

When working with CloudFormation, AWS recommends not to give explicit names to resources and let CloudFormation name them for you. This has several advantages: It’s harder for attackers to guess resource names such as S3 buckets or DynamoDB tables. You ca[...]

TL;DR To make an AppSync DynamoDB resolver throw exceptions on conditional check errors, we need to check $context.error in the response mapping template ourselves. Like this: #if ( $ctx.error ) #if ( $ctx.error.type.equals("DynamoDB:ConditionalCheckFaile[...]