Troubleshoot "Stack CDKToolkit already exists"

If you are deploying an Amplify Gen 2 app for the first time and have previously bootstrapped your AWS account to work with the AWS Cloud Development Kit (AWS CDK), and you encounter the following error in the Amplify Console:

Build error!
Stack [CDKToolkit] already exists

You can mitigate by manually updating your CDKToolkit stack using the browser-based AWS CloudShell:

cdk bootstrap aws://$(aws sts get-caller-identity --query Account --output text)/$AWS_REGION

Or by running bootstrap using the AWS CDK CLI from your terminal:

npx aws-cdk@latest bootstrap aws://<your-aws-account-id>/<your-aws-region>

If you continue to experience this issue after applying the workaround noted above, please file an issue in the GitHub repository for Amplify Backend.