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title AWS Lambda Backend
sidebar_position 13

The gateway can invoke AWS Lambda functions as backends, translating HTTP requests into Lambda invocations and returning the function response to the client.

Overview

When Lambda is enabled on a route, the Lambda handler replaces the standard HTTP reverse proxy as the innermost handler. Incoming HTTP requests are converted to an API Gateway-style JSON payload and sent to the configured Lambda function via the AWS SDK.

Configuration

routes:
  - id: serverless-api
    path: /api/compute
    path_prefix: true
    lambda:
      enabled: true
      function_name: my-api-handler
      region: us-west-2
      max_retries: 2
Field Type Default Description
enabled bool false Enable Lambda backend for this route
function_name string required AWS Lambda function name or ARN
region string us-east-1 AWS region for the Lambda function
max_retries int 0 Maximum retry attempts for failed invocations

How It Works

Request Translation

The handler converts HTTP requests into a JSON payload matching the API Gateway proxy integration format:

GET requests:

{
  "httpMethod": "GET",
  "path": "/api/compute/data",
  "queryParameters": {"key": ["value"]},
  "headers": {"Content-Type": "application/json"},
  "pathParameters": {}
}

POST/PUT/DELETE requests:

{
  "httpMethod": "POST",
  "path": "/api/compute/data",
  "headers": {"Content-Type": "application/json"},
  "body": "{\"name\": \"example\"}",
  "pathParameters": {}
}

Response Handling

  • Successful invocations return 200 with the Lambda function's payload as application/json.
  • Function errors (non-null FunctionError) return 502 with the error payload.
  • SDK errors (network failures, permissions) return 502 with an error message.

AWS Authentication

The handler uses the default AWS SDK credential chain (aws-sdk-go-v2/config.LoadDefaultConfig). Credentials are resolved from (in order):

  1. Environment variables (AWS_ACCESS_KEY_ID, AWS_SECRET_ACCESS_KEY)
  2. Shared credentials file (~/.aws/credentials)
  3. IAM instance profile / ECS task role / IRSA (Kubernetes)

Mutual Exclusions

Lambda replaces the proxy as the innermost handler. It is mutually exclusive with:

  • backends, service, upstream (standard proxy targets)
  • echo, static, fastcgi, sequential, aggregate
  • amqp, pubsub

All upstream middleware (auth, rate limiting, WAF, etc.) still applies to Lambda routes.

Admin API

GET /lambda

Returns per-route Lambda stats:

{
  "serverless-api": {
    "function_name": "my-api-handler",
    "total_requests": 5000,
    "total_errors": 12,
    "total_invokes": 5000
  }
}

Validation

  • function_name is required when enabled
  • Lambda is mutually exclusive with other innermost handlers (backends, static, echo, fastcgi, sequential, aggregate, amqp, pubsub)