Praneeta Prakash for AWS

Posted on Sep 10

AWS CDK in August 2025

#devtools #infrastructureascode #cdk #typescript

Major Features
Notable Fixes
Community Spotlight
- Community Content
AWS content updates
Want to be more involved?
Getting Started Resources

Welcome to the AWS CDK monthly update for August 2025! This month brought significant enhancements across the CDK ecosystem, with major improvements to developer experience, new service integrations, and enhanced deployment capabilities. Let's dive into the key updates that will help you build better cloud applications.

Major Features

Amazon Bedrock Guardrails L2 Construct (Alpha)

We're excited to introduce L2 constructs for Amazon Bedrock Guardrails, making it easier to implement responsible AI practices in your applications. This new alpha feature allows you to define content filters, topic restrictions, and safety policies directly in your CDK code.

import { Guardrail } from '@aws-cdk/aws-bedrock-alpha'; 
const guardrail = new Guardrail(this, 'MyGuardrail', { 
  name: 'content-safety-guardrail', 
  description: "'Guardrail for content safety', "
  contentPolicyConfig: { 
    filtersConfig: [{ 
      type: 'HATE', 
      inputStrength: 'HIGH', 
      outputStrength: 'HIGH' 
    }] 
  }, 
  topicPolicyConfig: { 
    topicsConfig: [{ 
      name: 'investment-advice', 
      definition: 'Investment advice and financial recommendations', 
      type: 'DENY' 
    }] 
  } 
});

While this is supported in the native CDK library, you can explore additional CDK constructs built specially for Gen AI use cases here.

ECS Native Blue/Green Deployments

ECS services now support native blue/green deployments through L2 constructs, enabling zero-downtime deployments with automatic rollback capabilities.

import { FargateService, AlternateTargetConfiguration } from 'aws-cdk-lib/aws-ecs'; 
const service = new FargateService(this, 'MyService', { 
  cluster, 
  taskDefinition, 
  alternateTargetConfiguration: new AlternateTargetConfiguration({ 
    containerName: 'web', 
    containerPort: 80, 
    listenerPort: 8080 
  }) 
});

Enhanced CLI Experience with Interactive Feature Flags

The CDK CLI now provides an interactive experience for managing feature flags, making it easier to configure and understand the impact of different CDK features. Read more here.

$ cdk flags --unstable=flags --set --recommended --all 
Feature Flag                              Recommended Value            User Value 
* @aws-cdk/...                              true                         false 
* @aws-cdk/...                              true                         false 
* @aws-cdk/...                              true                         <unset> 
  Synthesizing... 
    Resources 
    [~] AWS::S3::Bucket MyBucket 
    └─ [~] Properties 
        └─ [~] Encryption 
                ... 
    Number of stacks with differences: 2 
  Do you want to accept these changes? (y/n) y 
  Resynthesizing...

Notable Fixes

S3 Deployment: Fixed intermittent CloudFront invalidation errors during deployments
EKS: Resolved Helm command execution issues with ECR public registry authentication
Lambda: Improved startup time for large applications by optimizing lazy loading
CloudWatch: Fixed AlarmRule.concat to properly handle empty operands
Step Functions: Corrected Bedrock Agent service IAM prefix mapping

Community Spotlight

Big shout-outs to phuhung273 for 3 merged PRs in August! They made multiple high impact contributions including Docker build networking enhancements (#34725), CloudWatch alarm rule fixes (#34757), and comprehensive RDS engine version updates across PostgreSQL, SQL Server, and MySQL (#35013).

We also celebrate mazyu36 for their outstanding work with 3 impactful contributions - modernizing RDS VPC security group lookups (#34906) and improving EKS documentation structure (#34783).

Special recognition goes to badmintoncryer (#34962), xuxey (#35223), richarddotcodes (#35025), maramure (#35060), and jaw111 (#34712) for their valuable contributions spanning ECS volume optimization, S3 Tables security policies, cross-region VPC endpoints, WebSocket API management, and SNS filtering capabilities.

Community Content

Kenta Goto wrote an extremely helpful article on “How to choose validation approaches in AWS CDK”.
Jeroen Reijn has tips on Enabling AWS Budget Notifications with SNS using AWS CDK
Lee Gilmore compares AWS CDK Blueprints vs Custom Constructs vs Aspects in this article.

AWS content updates

Here are some recent blogposts that demonstrate use of CDK to build various applications on AWS.

Want to be more involved?

The CDK team runs community meetings every quarter to discuss new features, best practices and highlight community-built projects. We publish videos here in a community run YouTube channel and have a 10k+ active community discussing all things CDK and AWS in CDK.dev Community Slack. Join us!

We are also looking for community reviewers to help us move faster on PRs. Check out open PRs here and provide your review and guidance to other CDK contributors.

Getting Started Resources

Have feedback or questions about these updates? Join the conversation in our GitHub Discussions.

Happy building! 🚀

The AWS CDK Team

DEV Community