Skill

adapter-aws-lambda

Name: adapter-aws-lambda
Author: tRPC

deploy tRPC APIs on AWS Lambda

Published by tRPC Updated Jul 18

Covers Backend tRPC API Development AWS

Description

Deploy tRPC on AWS Lambda with awsLambdaRequestHandler() from @trpc/server/adapters/aws-lambda for API Gateway v1 (REST, APIGatewayProxyEvent) and v2 (HTTP, APIGatewayProxyEventV2), and Lambda Function URLs. Enable response streaming with awsLambdaStreamingRequestHandler() wrapped in awslambda.streamifyResponse(). CreateAWSLambdaContextOptions provides event and context for context creation.

SKILL.md

tRPC — Adapter: AWS Lambda

Setup

// server.ts
import { initTRPC } from '@trpc/server';
import type { CreateAWSLambdaContextOptions } from '@trpc/server/adapters/aws-lambda';
import { awsLambdaRequestHandler } from '@trpc/server/adapters/aws-lambda';
import type { APIGatewayProxyEventV2 } from 'aws-lambda';
import { z } from 'zod';

const t = initTRPC.create();

const appRouter = t.router({
  greet: t.procedure
    .input(z.object({ name: z.string() }))
    .query(({ input }) => ({ greeting: `Hello, ${input.name}!` })),
});

export type AppRouter = typeof appRouter;

const createContext = ({
  event,
  context,
}: CreateAWSLambdaContextOptions<APIGatewayProxyEventV2>) => ({
  event,
  lambdaContext: context,
});

export const handler = awsLambdaRequestHandler({
  router: appRouter,
  createContext,
});

Core Patterns

API Gateway v1 (REST) handler

import type { CreateAWSLambdaContextOptions } from '@trpc/server/adapters/aws-lambda';
import { awsLambdaRequestHandler } from '@trpc/server/adapters/aws-lambda';
import type { APIGatewayProxyEvent } from 'aws-lambda';
import { appRouter } from './router';

const createContext = ({
  event,
  context,
}: CreateAWSLambdaContextOptions<APIGatewayProxyEvent>) => ({
  user: event.requestContext.authorizer?.claims,
});

export const handler = awsLambdaRequestHandler({
  router: appRouter,
  createContext,
});

Use APIGatewayProxyEvent for REST API (v1 payload format) and APIGatewayProxyEventV2 for HTTP API (v2 payload format).

Response streaming with awsLambdaStreamingRequestHandler

/// <reference types="aws-lambda" />
import type { CreateAWSLambdaContextOptions } from '@trpc/server/adapters/aws-lambda';
import { awsLambdaStreamingRequestHandler } from '@trpc/server/adapters/aws-lambda';
import type { APIGatewayProxyEventV2 } from 'aws-lambda';
import { appRouter } from './router';

const createContext = ({
  event,
  context,
}: CreateAWSLambdaContextOptions<APIGatewayProxyEventV2>) => ({});

export const handler = awslambda.streamifyResponse(
  awsLambdaStreamingRequestHandler({
    router: appRouter,
    createContext,
  }),
);

Response streaming is supported for Lambda Function URLs and API Gateway REST APIs (with responseTransferMode: STREAM). The awslambda namespace is provided by the Lambda execution environment.

Streaming async generator procedure

import { initTRPC } from '@trpc/server';

const t = initTRPC.create();

export const appRouter = t.router({
  countdown: t.procedure.query(async function* () {
    for (let i = 10; i >= 0; i--) {
      await new Promise((resolve) => setTimeout(resolve, 500));
      yield i;
    }
  }),
});

Pair with httpBatchStreamLink on the client for streamed responses.

Limiting batch size with maxBatchSize

import { awsLambdaRequestHandler } from '@trpc/server/adapters/aws-lambda';
import { appRouter } from './router';

export const handler = awsLambdaRequestHandler({
  router: appRouter,
  createContext,
  maxBatchSize: 10,
});

Requests batching more than maxBatchSize operations are rejected with a 400 Bad Request error. Set maxItems on your client's httpBatchLink to the same value to avoid exceeding the limit.

Common Mistakes

HIGH Using httpBatchLink with per-procedure API Gateway resources

Wrong:

// API Gateway has a separate resource for each procedure
// e.g., /getUser, /createUser
// Client uses:
import { httpBatchLink } from '@trpc/client';

httpBatchLink({ url: 'https://api.example.com' });
// Batch request to /getUser,createUser → 404

Correct:

import { httpBatchLink, httpLink } from '@trpc/client';

// Option A: Single catch-all resource (e.g., /{proxy+})
httpBatchLink({ url: 'https://api.example.com' });

// Option B: Per-procedure resources with httpLink (no batching)
httpLink({ url: 'https://api.example.com' });

httpBatchLink sends multiple procedure names in the URL path (e.g., getUser,createUser). If API Gateway routes are per-procedure, the combined path does not match any resource and returns 404. Use a single catch-all resource or switch to httpLink.

Source: www/docs/server/adapters/aws-lambda.md

HIGH Forgetting streamifyResponse wrapper for streaming

Wrong:

export const handler = awsLambdaStreamingRequestHandler({
  router: appRouter,
  createContext,
});

Correct:

export const handler = awslambda.streamifyResponse(
  awsLambdaStreamingRequestHandler({
    router: appRouter,
    createContext,
  }),
);

awsLambdaStreamingRequestHandler requires wrapping with awslambda.streamifyResponse() to enable Lambda response streaming. Without it, Lambda treats the handler as a standard buffered response.

Source: www/docs/server/adapters/aws-lambda.md

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