I had been working on a client project where I built the GraphQL backend for a new social network using primarily AppSync, Lambda and DynamoDB. One of the features of the app was to support private messaging between two users. To allow either user to fetch their chat messages in chronological descending order, I modelled … AppSync: how to compare strings lexicographically in VTL Read More » Liked this article? Support me on Patreon and get direct help from me via a private Slack channel or 1-2-1 mentori[...]

Hi, welcome to another weekly update. Production-Ready Serverless workshop goes virtual! Starting from May 4th, I will be running a 4-week instructor-led workshop that teaches you everything you need to know to build a production-ready serverless application. It’s based on the same demo app as my Manning course, but all the code has been completely … Weekly update 44 Read More » Liked this article? Support me on Patreon and get direct help from me via a private Slack channel or 1-2-1 mentoring. Hi,[...]

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:ConditionalCheckFailedException") ) $util.error("your error message") #else $util.error($ctx.error.message, $ctx.error.type) #end #end $utils.toJson($context.result) And now, the longer version. The problem AppSync lets us perform DynamoDB … AppSync: how to error on DynamoDB[...]

Have you been wondering about serverless but just don’t know how and where to start? Maybe you’re already building stuff with serverless, but don’t know if you’re doing it right? Are you unsure about the best practices for testing, monitoring and how to choose between similar services like SNS and EventBridge?   I have just … Skill up your serverless game with my new instructor-led online workshop Read More » Liked this article? Support me on Patreon and get direct help from me via a private Slack chann[...]

So you have built a serverless application, that, amongst other things, lets you upload images and files to S3. The set-up is very simple: API Gateway, Lambda and S3. It took you no time to implement and it works like a dream. You pat yourself on the back for another job well done. Until one … Hit the 6MB Lambda payload limit? Here’s what you can do. Read More » Liked this article? Support me on Patreon and get direct help from me via a private Slack channel or 1-2-1 mentoring. Hi, my name is Yan C[...]