Support multi-backend composition (merge) for Amplify Gen 2 monorepos

[RestingState]

Environment information

System:
  OS: Windows 11 10.0.26200
  CPU: (16) x64 13th Gen Intel(R) Core(TM) i7-13620H
  Memory: 5.92 GB / 15.73 GB
Binaries:
  Node: 24.14.0 - C:\Users\denys\AppData\Local\mise\installs\node\24.14.0\node.EXE
  Yarn: undefined - undefined
  npm: 11.9.0 - C:\Users\denys\AppData\Local\mise\installs\node\24.14.0\npm.CMD
  pnpm: undefined - undefined
NPM Packages:
  @aws-amplify/auth-construct: 1.11.2
  @aws-amplify/backend: 1.22.0
  @aws-amplify/backend-ai: Not Found
  @aws-amplify/backend-auth: 1.9.3
  @aws-amplify/backend-cli: 1.8.2
  @aws-amplify/backend-data: 1.6.4
  @aws-amplify/backend-function: 1.18.0
  @aws-amplify/backend-output-storage: 1.3.4
  @aws-amplify/backend-secret: 1.4.2
  @aws-amplify/backend-storage: 1.4.3
  @aws-amplify/cli-core: 2.2.4
  @aws-amplify/client-config: 1.10.1
  @aws-amplify/data-construct: 1.17.0
  @aws-amplify/data-schema: 1.22.2
  @aws-amplify/deployed-backend-client: 1.8.1
  @aws-amplify/form-generator: 1.2.6
  @aws-amplify/model-generator: 1.2.2
  @aws-amplify/platform-core: 1.11.0
  @aws-amplify/plugin-types: 1.12.0
  @aws-amplify/sandbox: 2.1.4
  @aws-amplify/schema-generator: 1.4.1
  @aws-cdk/toolkit-lib: 1.16.0
  aws-amplify: 6.16.3
  aws-cdk-lib: 2.235.0
  typescript: 6.0.2
No AWS environment variables
No CDK environment variables

Describe the feature

I’d like Amplify Gen 2 to support composing/merging two or more backends within a single monorepo to enable a true microservices architecture.

Today, each backend app produces its own amplify_outputs.json, but there is no clear built-in mechanism for merging or consuming multiple backend outputs in one frontend app. This makes multi-backend setups ambiguous and difficult to implement safely.

Requested feature options (either would help, both would be ideal):

1. Native multi-backend support in Amplify Gen 2 (e.g., official merge/composition mechanism for multiple backend apps and outputs).
2. Official end-to-end guide from the Amplify team for implementing microservice architecture in Gen 2 monorepos (backend boundaries, auth sharing, outputs strategy, frontend integration patterns, deployment orchestration, and best practices).

Use case

Our current “main” Amplify backend has grown very large (close to 100 Lambda functions plus additional resources such as SQS, resolvers, EventBridge rules, etc.). As a result, deploy/sandbox cycles are slow, and ampx sandbox compilation/typechecking takes too long.

We want to split domains (for example, telephony) into separate backend services inside the same monorepo while keeping a primary backend for shared concerns (such as Cognito). The missing piece is an official and reliable way to combine/consume multiple backends from the frontend and operate them as one system.

This feature (or official guidance) would significantly improve:

• Build and deploy performance
• Team ownership boundaries
• Scalability of large Gen 2 projects
• Clarity and confidence when adopting microservice-style architecture in Amplify