AWS Lambda + API Gateway Adapter

AWS Lambda adapter

The AWS Lambda adapter is supported for API Gateway REST API(v1) and HTTP API(v2), and Lambda Function URL use cases.

httpBatchLink requires the router to work on a single API Gateway Resource (as shown in the example). If you'd like to have a Resource per procedure, you can use the httpLink instead (more info).

Example app

Description	Links
API Gateway with NodeJS client.	Source

How to add tRPC

1. Install deps

bash
yarn add @trpc/server

bash
yarn add @trpc/server

2. Create a tRPC router

Implement your tRPC router. A sample router is given below:

server.ts
ts
import { initTRPC } from '@trpc/server';
import { z } from 'zod';
export const t = initTRPC.create();
const appRouter = t.router({
  getUser: t.procedure.input(z.string()).query((opts) => {
    opts.input; // string
    return { id: opts.input, name: 'Bilbo' };
  }),
});
// export type definition of API
export type AppRouter = typeof appRouter;

server.ts
ts
import { initTRPC } from '@trpc/server';
import { z } from 'zod';
export const t = initTRPC.create();
const appRouter = t.router({
  getUser: t.procedure.input(z.string()).query((opts) => {
    opts.input; // string
    return { id: opts.input, name: 'Bilbo' };
  }),
});
// export type definition of API
export type AppRouter = typeof appRouter;

3. Use the Amazon API Gateway adapter

tRPC includes an adapter for API Gateway out of the box. This adapter lets you run your routes through the API Gateway handler.

server.ts
ts
import { CreateAWSLambdaContextOptions, awsLambdaRequestHandler } from '@trpc/server/adapters/aws-lambda';
const appRouter = /* ... */;
// created for each request
const createContext = ({
  event,
  context,
}: CreateAWSLambdaContextOptions<APIGatewayProxyEventV2>) => ({}) // no context
type Context = Awaited<ReturnType<typeof createContext>>;
export const handler = awsLambdaRequestHandler({
  router: appRouter,
  createContext,
})

server.ts
ts
import { CreateAWSLambdaContextOptions, awsLambdaRequestHandler } from '@trpc/server/adapters/aws-lambda';
const appRouter = /* ... */;
// created for each request
const createContext = ({
  event,
  context,
}: CreateAWSLambdaContextOptions<APIGatewayProxyEventV2>) => ({}) // no context
type Context = Awaited<ReturnType<typeof createContext>>;
export const handler = awsLambdaRequestHandler({
  router: appRouter,
  createContext,
})

Build & deploy your code, now use your API Gateway URL to call your function.

Endpoint	HTTP URI
getUser	GET https://<execution-api-link>/getUser?input=INPUT where INPUT is a URI-encoded JSON string.

A word about payload format version

API Gateway has two different event data formats when it invokes a Lambda. For REST APIs they should be version "1.0"(APIGatewayProxyEvent), but you can choose which for HTTP APIs by stating either version "1.0" or "2.0".

• Version 1.0: APIGatewayProxyEvent
• Version 2.0: APIGatewayProxyEventV2

To infer what version you might have, supply the context as following:

ts
function createContext({
  event,
  context,
}: CreateAWSLambdaContextOptions<APIGatewayProxyEvent>) {
  ...
}
// CreateAWSLambdaContextOptions<APIGatewayProxyEvent> or CreateAWSLambdaContextOptions<APIGatewayProxyEventV2>

ts
function createContext({
  event,
  context,
}: CreateAWSLambdaContextOptions<APIGatewayProxyEvent>) {
  ...
}
// CreateAWSLambdaContextOptions<APIGatewayProxyEvent> or CreateAWSLambdaContextOptions<APIGatewayProxyEventV2>

Read more here about payload format version

AWS Lambda Response Streaming Adapter

AWS Lambda supports streaming responses to clients.

Response streaming is only supported for Lambda Function URLs. You can not use API Gateway to stream responses. Read more here about response streaming.

Example app

Description	Links
Lambda Function URL with NodeJS client.	Source

Response Streaming

The signature of a streaming handler is different from the default handler. The streaming handler additonally receives a writable stream parameter, responseStream, besides the default node handler parameters, event and context. To indicate that Lambda should stream your responses, you must wrap your function handler with the awslambda.streamifyResponse() decorator.

Note that the awslambda namespace is automatically provided by the Lambda execution environment. You can import the types from @types/aws-lambda to augment the global namespace with the awslambda namespace.

server.ts
ts
import { awsLambdaStreamingRequestHandler } from '@trpc/server/adapters/aws-lambda';
import type { StreamifyHandler } from 'aws-lambda';
const appRouter = router({
  iterable: publicProcedure.query(async function* () {
    for (let i = 0; i < 10; i++) {
      await new Promise((resolve) => setTimeout(resolve, 500));
      yield i;
    }
  }),
});
export const handler = awslambda.streamifyResponse(
  awsLambdaStreamingRequestHandler({
    router: appRouter,
    /* ... */
  }),
);

server.ts
ts
import { awsLambdaStreamingRequestHandler } from '@trpc/server/adapters/aws-lambda';
import type { StreamifyHandler } from 'aws-lambda';
const appRouter = router({
  iterable: publicProcedure.query(async function* () {
    for (let i = 0; i < 10; i++) {
      await new Promise((resolve) => setTimeout(resolve, 500));
      yield i;
    }
  }),
});
export const handler = awslambda.streamifyResponse(
  awsLambdaStreamingRequestHandler({
    router: appRouter,
    /* ... */
  }),
);