Detailed AWS setup

To work locally all you need is Node, any additional supported runtimes you plan to use, and the Architect CLI.

AWS deployment requirements

  1. Node.js for Architect
  2. Any additional supported runtimes you plan to use in your application
  3. AWS credentials
  4. Architect CLI

Runtime environments

Architect supports the following runtimes for composing your application’s business logic:

  • Node.js: >= 16.x using npm
    • Unless otherwise specified in your project manifest, Node.js 20.x is the default runtime for new functions
  • Python: >= 3.8 using pip3
    • Unless otherwise specified in your project manifest, Python 3.12 is the default Python runtime
  • Ruby: 3.2 using bundle
  • Deno: 1.6.x (under development)

⚠️ Working locally with the Sandbox requires target runtimes to be available in your $PATH.

Additionally, other standard AWS-managed runtimes are supported in Architect applications (but may not be supported in Sandbox). Learn more about Architect’s runtime support.

Architect also supports any custom runtime in using either Lambda Layers or Lambda container images.

Change a project’s default runtime by specifying an explicit environment or an alias in app.arc with the @aws pragma.


# version pins the default runtime to Python 3.8
runtime python3.8
# always run the latest supported version of Python
runtime python

ℹ️ This setting can be overridden on a per-function basis with config.arc.


You’ll need an Amazon Web Services account and credentials set up on your development machine and / or CI systems. If you haven’t yet set it up, here’s a useful guide for Configuring the AWS CLI.

In the context of a deployment tool, Architect requires account credentials with IAM AdministratorAccess privileges. In turn, Architect will create and attach least-privilege IAM roles to runtime resources within your application, ensuring strict security boundaries by default.

ℹ️ While it is possible to limit Architect’s deployment credentials to specific IAM and CloudFormation privileges, such an exercise would only be performative. Credentials capable of creating IAM roles can grant and attach new roles with AdministratorAccess.

On *nix systems AWS Credentials are listed in:


Or on Windows systems:


If that file doesn’t exist, create it, and add something like the following (assuming you have multiple AWS accounts):




While it is recommended to explicitly declare your application’s AWS profile and region in the @aws pragma of your project’s manifest, you may also set a (default) profile and region with the AWS_PROFILE + AWS_REGION environment variables.

Install Architect

The following command uses npm, the package manager for Node.js.

To create an entirely new Architect project:

npm init @architect ./testapp
npm init "@architect" ./testapp

To install Architect locally into an existing project:

npm i -D @architect/architect
npm i -D "@architect/architect"

Or you can install Architect globally, enabling you to use Architect from any directory on your computer.

npm i -g @architect/architect

Interacting with AWS services

Each Lambda runtime version includes its own built-in version of the AWS SDK. However, due to ongoing performance and developer ergonomics issues with the AWS SDK, we recommend utilizing the community-driven aws-lite SDK.

Using aws-lite

Since the AWS SDK is an extremely large library, we strongly recommend you do not ship your own version as a dependency, either in full or as a bundle. Doing so may have some of the following unintended side effects:

  • Slower Lambda coldstart and / or invocation
  • Reduced available code payload size
  • Possibly increased difficulty debugging (in the case of bundles)

Instead, we recommend interacting with AWS services via aws-lite where possible, as it is 2-5x faster, and hundreds of megabytes smaller than the AWS SDK. Learn more here.

Where that is not possible, we recommend using AWS Lambda’s provided, non-bundled version of the AWS SDK. See below for details.

Architect’s AWS SDK strategy

A core goal of Architect is to make building Functional Web Apps simpler, and an important aspect of that objective is to help (automatically) manage the many dependencies in use across your Lambdas, whether your project has one or one hundred of them.

However, in the of AWS SDK, AWS manages that dependency within the Lambda environment. For the aforementioned reasons, Architect does not attempt to automatically manage or include any version of AWS SDK in the resources it manages on your behalf.

Practically speaking, that means if you rely on Architect’s Lambda treeshaking feature – which scans your Lambda code and automatically installs required or imported dependencies at deploy-time – versions of the AWS SDK will not be automatically added to your Lambda dependencies by Architect (as it is already expected to be present in the Lambda environment).

Architect will, however, attempt to provide helpful warnings where possible. For example: if your nodejs18.x Lambda imports aws-sdk, the now-deprecated v2 that is not built into the Lambda container, Architect will warn you of this during deployment.

Node.js AWS SDK versions

AWS has opted Node.js developers into a migration from AWS SDK v2 (aws-sdk, now deprecated)) to v3 (@aws-sdk/*):

  • Lambda nodejs18.x and greater use AWS SDK v3 (@aws-sdk/*)
  • Lambda nodejs16.x and prior use AWS SDK v2 (aws-sdk)
    • The last Lambda runtime to use SDK v2, nodejs16.x, is deprecated mid-2024

Migrating from AWS SDK v2 to v3 represents a meaningful change, and should be investigated thoroughly and with care. Key interfaces have been retired (such as .promise()), and some core SDK methods have changed significantly. (Example: S3.GetObject no longer returns a Buffer.)

Instead of adopting the forced breaking changes of a migration to AWS SDK v3, we instead recommend migrating (and contributing, where possible) to the aws-lite SDK.

Architect maintains an ongoing commitment to backward compatibility wherever possible; as such, @architect/functions users can likely safely and reliably upgrade handlers in most cases. For additional details, please refer to the Architect upgrade guide.