AWS Lambda

The Lambda adapter accepts API Gateway HTTP API payload v2.0, API Gateway REST API payload v1.0, and Lambda Function URLs without configuration. It handles base64 bodies, v2 cookies, v1 multiValueHeaders, and forwards method, path, query, and headers into a standard Request.

When to choose Lambda

• You already run on AWS and want IAM-integrated invocation.
• You want per-request billing without managing a server.
• You need long timeouts (up to 15 minutes) or larger memory than edge functions allow.

Install

The adapter ships with @daloyjs/core. For deployment, use AWS SAM, CDK, the Serverless Framework, or any IaC of your choice.

Function URL or API Gateway HTTP API

// src/lambda.ts
import { toLambdaHandler } from "@daloyjs/core/lambda";
import { app } from "./server.js";

export const handler = toLambdaHandler(app);

Streaming responses

Lambda supports response streaming via awslambda.streamifyResponse. Use the streaming variant of the adapter when you need to flush headers and bytes incrementally (Server-Sent Events, large downloads).

// src/lambda-stream.ts
import { toLambdaStreamHandler } from "@daloyjs/core/lambda";
import { app } from "./server.js";

export const handler = toLambdaStreamHandler(app);
// Uses awslambda.streamifyResponse + HttpResponseStream.from internally.

SAM template

DaloyJS requires Node 24 LTS or Node 26+ (engines.node: "^24.0.0 || >=26.0.0"). Use the nodejs24.x managed runtime where available, or ship a container image (see Lambda Web Adapter below) if your region's runtime catalog is older.

# template.yaml
AWSTemplateFormatVersion: "2010-09-09"
Transform: AWS::Serverless-2016-10-31

Resources:
  Api:
    Type: AWS::Serverless::Function
    Properties:
      CodeUri: dist/
      Handler: lambda.handler
      Runtime: nodejs24.x
      MemorySize: 1024
      Timeout: 30
      FunctionUrlConfig:
        AuthType: NONE
        InvokeMode: BUFFERED   # or RESPONSE_STREAM for streaming

Lambda Web Adapter (container deployments)

If you prefer to ship a container image and keep the Node adapter, the AWS Lambda Web Adapter translates Lambda invocations to plain HTTP. Useful when you want one image for both ECS and Lambda.

FROM public.ecr.aws/awsguru/aws-lambda-adapter:0.9.0 AS adapter
FROM node:24-slim
COPY --from=adapter /lambda-adapter /opt/extensions/lambda-adapter
WORKDIR /var/task
COPY package.json pnpm-lock.yaml ./
RUN corepack enable && pnpm install --prod --frozen-lockfile
COPY dist ./dist
ENV PORT=8080 AWS_LWA_PORT=8080
CMD ["node", "dist/server.js"]

Gotchas

• Callback-style handlers ((event, context, callback) => ...) are not supported on supported Node versions. Always use async handlers. The DaloyJS adapter does.
• For Function URLs with streaming, set InvokeMode: RESPONSE_STREAM and use toLambdaStreamHandler.
• Cold starts: prefer the Node adapter on provisioned concurrency or use a container with the Web Adapter for warmer reuse.
• Since 1.3.7 the adapter answers 400 when the event's Host header is not a plain host[:port] or bracketed IPv6 literal (for example one containing \ / ? # @ % or whitespace). The host is spliced into the request URL, so such a value could otherwise move bytes into the path that except() and other middleware match on.
• X-Forwarded-Proto is honoured only when the App declares a proxy (behindProxy set and not "none"), and then only as http or https, read from the last comma-separated entry (the one the nearest proxy appended). Otherwise the scheme is https, so a client-sent header can't downgrade the URL your app sees (since 1.5.4; before that, the first entry was honoured without a declared proxy).

See also

• Adapters overview
• Netlify Functions: v1 still uses the same Lambda event shape if you need it.
• Streaming (SSE & NDJSON)