AWS Lambda streaming

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An example on how to enable streaming for Lambda functions.

sst.config.ts

{
  streaming: true
}

Use the awslambda.streamifyResponse function to wrap your handler. The awslambda global is provided by the Lambda execution environment at runtime, and SST provides it automatically during sst dev as well. For TypeScript types, importing from @types/aws-lambda will augment the global namespace.

index.ts

export const handler = awslambda.streamifyResponse(
  async (event, stream) => {
    stream = awslambda.HttpResponseStream.from(stream, {
      statusCode: 200,
      headers: {
        "Content-Type": "text/plain; charset=UTF-8",
        "X-Content-Type-Options": "nosniff",
      },
    });

    stream.write("Hello ");
    await new Promise((resolve) => setTimeout(resolve, 3000));
    stream.write("World");

    stream.end();
  },
);

sst.config.ts

const fn = new sst.aws.Function("MyFunction", {
  url: true,
  streaming: true,
  timeout: "15 minutes",
  handler: "index.handler",
});

View the full example.