AWS SDK JS V3 Usage

AWSOfficialPublished by AWS

Skill
Tool integration
Cloud and DevOps
Apache-2.0
Medium risk

From the author

AWS SDK for JavaScript v3 development patterns. Use when writing JavaScript or TypeScript code that uses AWS services via @aws-sdk/* packages (aws-sdk-js-v3), or when asked about schemas, runtime validation, serialization, or code generation in the context of the JS/TS AWS SDK.

— the description by AWS

AutoGineer summary

Written by AutoGineer from the skill’s own files, not by the author

This skill provides a comprehensive guide to the AWS SDK for JavaScript v3 (@aws-sdk/*). It covers modular package structure, client configuration, credential management, streaming data handling, pagination, and performance optimization. It includes patterns for common services like S3 and DynamoDB, error handling, and integration strategies for Node.js and Lambda environments.

What it does

Explains the modular package structure of AWS SDK v3.
Provides patterns for client configuration and credential providers.
Demonstrates efficient handling of streaming responses to prevent socket exhaustion.
Offers guidance on using paginators and the DynamoDB DocumentClient.
Details error handling, middleware usage, and performance tuning for parallel workloads.
Outlines best practices for Lambda function integration and TypeScript usage.

When to use it

When writing JavaScript or TypeScript applications that interact with AWS services.
When migrating from older SDK versions to v3.
When optimizing AWS service interactions for performance or bundle size.
When implementing complex authentication flows like STS AssumeRole or OIDC.
When troubleshooting SDK-related errors or connection issues.

Advantages

Promotes smaller bundle sizes through modular imports.
Ensures robust resource management with proper stream handling.
Provides standardized patterns for common AWS operations.
Facilitates secure and flexible credential management.
Helps avoid common pitfalls like socket exhaustion and memory leaks.

Usage examples

“How do I initialize an S3 client in AWS SDK v3?”: The agent provides the code to import S3Client and GetObjectCommand, showing how to instantiate the client with a region and send a command.
“How can I read an S3 object body without causing memory issues?”: The agent explains how to use Body.transformToString() or Body.transformToByteArray() and emphasizes the importance of destroying the stream.
“How do I assume an IAM role using the SDK?”: The agent demonstrates the use of fromTemporaryCredentials from the @aws-sdk/credential-providers package.
“What is the best way to list all tables in DynamoDB?”: The agent provides an example using the paginateListTables function with an async iterator.

Install

Download the skill as a ZIP:
https://autogineer.com/agent-skills/aws/aws-sdk-js-v3-usage/download

Unzip it into the cross-client skills folder of your project:

mkdir -p .agents/skills && unzip aws-sdk-js-v3-usage.zip -d .agents/skills

Documentation by AWS

Do not use emojis in any code, comments, or output when this skill is active.

AWS SDK for JavaScript v3

Package Structure

@aws-sdk/client-* — one per service, generated by smithy-typescript; one-to-one with AWS services and operations
@aws-sdk/lib-* — higher-level helpers (e.g. lib-dynamodb, lib-storage)
@aws-sdk/* (no prefix) — utility packages (mostly internal; don't import deep paths)

Always import from the package root:

import { S3Client } from "@aws-sdk/client-s3"; // correct
// NOT: import { S3Client } from "@aws-sdk/client-s3/dist-cjs/S3Client"

Two Client Styles

Bare-bones (preferred — smaller bundle):

import { S3Client, GetObjectCommand } from "@aws-sdk/client-s3";
const client = new S3Client({ region: "us-east-1" });
const output = await client.send(new GetObjectCommand({ Bucket: "b", Key: "k" }));

Aggregated (v2-style but NOT v2, larger bundle):

import { S3 } from "@aws-sdk/client-s3";
const client = new S3({ region: "us-east-1" });
const output = await client.getObject({ Bucket: "b", Key: "k" });

Client Configuration

No global config in v3 — pass config to each client. region is always required; set it explicitly or via AWS_REGION env var.

const config = { region: "us-east-1", maxAttempts: 5 };
const s3 = new S3Client(config);
const dynamo = new DynamoDBClient(config);

Do not read or mutate client.config after instantiation — it is a resolved form (e.g. region becomes an async function). See references/effective-practices.md.

For HTTP handler (NodeHttpHandler from @smithy/node-http-handler), retry strategy, endpoint details, logging, FIPS, dual-stack, protocol selection, and S3-specific options → see references/clients.md.

Credentials

All providers from @aws-sdk/credential-providers. Credentials are lazy and cached per client until ~5 min before expiry.

// Default chain (env → ini → IMDS/ECS) — use in most Node.js apps
const client = new S3Client({ credentials: fromNodeProviderChain() });

// Assume role (NOTE: fromTemporaryCredentials is correct for STS AssumeRole)
const client = new S3Client({
  credentials: fromTemporaryCredentials({ params: { RoleArn: "arn:aws:iam::123456789012:role/MyRole" } }),
});

// Named profile
const client = new S3Client({ profile: "my-profile" });

Share credentials and socket pool across multi-region clients:

const east = new S3Client({ region: "us-east-1" });
const { credentials, requestHandler } = east.config;
const west = new S3Client({ region: "us-west-2", credentials, requestHandler });

For all providers (Cognito, SSO, web identity, custom chains, STS region priority) → see references/credentials.md.

Streams (e.g. S3 GetObject Body)

Always read or discard streaming responses — unread streams leave sockets open (socket exhaustion):

const { Body } = await client.send(new GetObjectCommand({ Bucket: "b", Key: "k" }));
const str = await Body.transformToString();       // read as string
const bytes = await Body.transformToByteArray();  // read as Uint8Array
// or discard:
await (Body.destroy?.() ?? Body.cancel?.());

Streams can only be read once.

Paginators

Use paginate* functions instead of manual token handling:

import { DynamoDBClient, paginateListTables } from "@aws-sdk/client-dynamodb";

const client = new DynamoDBClient({});

const tableNames = [];
for await (const page of paginateListTables({ client }, {})) {
  // page contains a single paginated output.
  tableNames.push(...page.TableNames);
}

DynamoDB DocumentClient

Use @aws-sdk/lib-dynamodb to work with native JS types instead of AttributeValues:

import { DynamoDBClient } from "@aws-sdk/client-dynamodb";
import { DynamoDBDocumentClient, GetCommand, PutCommand } from "@aws-sdk/lib-dynamodb";

const client = DynamoDBDocumentClient.from(new DynamoDBClient({}));
await client.send(new PutCommand({ TableName: "T", Item: { id: "1", name: "Alice" } }));
const { Item } = await client.send(new GetCommand({ TableName: "T", Key: { id: "1" } }));

For marshall options, large numbers (NumberValue), pagination, and aggregated client → see references/dynamodb.md.

S3: Presigned URLs, Multipart Upload, Waiters

// Presigned GET URL
import { getSignedUrl } from "@aws-sdk/s3-request-presigner";
const url = await getSignedUrl(client, new GetObjectCommand({ Bucket: "b", Key: "k" }), { expiresIn: 3600 });

// Multipart upload (large files / streams)
import { Upload } from "@aws-sdk/lib-storage";
const upload = new Upload({ client, params: { Bucket: "b", Key: "k", Body: stream } });
await upload.done();

// Waiters
import { waitUntilObjectExists } from "@aws-sdk/client-s3";
await waitUntilObjectExists({ client, maxWaitTime: 120 }, { Bucket: "b", Key: "k" });

For presigned POST, signed headers, waiter options → see references/s3.md.

Error Handling

import { S3ServiceException } from "@aws-sdk/client-s3";

try {
  await client.send(new GetObjectCommand({ Bucket: "b", Key: "k" }));
} catch (e) {
  if (e?.$metadata) {
    // SDK service error — has $metadata.httpStatusCode, e.name, e.$response
    console.error(e.name, e.$metadata.httpStatusCode);
  }
}

Check e.name or instanceof for specific error types. See references/error-handling.md for full patterns.

For runtime validation, serialization to non-default formats, or questions about what schemas are in jsv3 → see references/schemas.md.

Performance: Parallel Workloads

// Configure maxSockets to match your parallel batch size
const client = new S3Client({
  requestHandler: { httpsAgent: { maxSockets: 50 } },
  cacheMiddleware: true, // skip if using custom middleware
});

Streaming deadlock warning: with limited sockets, don't await the request and stream body separately — chain them. See references/performance.md.

Middleware

Add custom logic to all commands on a client:

client.middlewareStack.add(
  (next, context) => async (args) => {
    console.log(context.commandName, args.input);
    const result = await next(args);
    return result;
  },
  { name: "MyMiddleware", step: "build", override: true }
);

Steps (in order): initialize → serialize → build → finalizeRequest → deserialize

Abort Controller

const { AbortController } = require("@aws-sdk/abort-controller");
const { S3Client, CreateBucketCommand } = require("@aws-sdk/client-s3");

const abortController = new AbortController();
const client = new S3Client(clientParams);

const requestPromise = client.send(new CreateBucketCommand(commandParams), {
  abortSignal: abortController.signal,
});

// The request will not be created if abortSignal is already aborted.
// The request will be destroyed if abortSignal is aborted before response is returned.
abortController.abort();

// This will fail with "AbortError" as abortSignal is aborted.
await requestPromise;

Lambda Best Practices

Initialize clients outside the handler (container reuse), make API calls inside. For one-time async setup, use a lazy init flag inside the handler:

import { S3Client } from "@aws-sdk/client-s3";

const client = new S3Client({}); // outside — reused across invocations

let ready = false;
export const handler = async (event) => {
  if (!ready) { await prepare(); ready = true; } // lazy one-time setup inside handler
  // ... API calls here
};

See references/lambda.md for Lambda layers and versioning.

Node.js Version Requirements

v3.968.0+ requires Node.js >= 20
v3.723.0+ requires Node.js >= 18

TypeScript

Response fields are typed as T | undefined by default. Use AssertiveClient from @smithy/types to remove | undefined, or NodeJsClient / BrowserClient to narrow streaming blob types. See references/typescript.md.

SigV4a (S3 Multi-Region Access Points)

S3 MRAP and certain other features require SigV4a. You must install and side-effect-import exactly one of:

@aws-sdk/signature-v4-crt — Node.js only, better performance
@aws-sdk/signature-v4a — Node.js + browsers, pure JS

import "@aws-sdk/signature-v4a"; // side-effect only — no exported values needed

See references/sigv4a.md for full details and MRAP ARN format.

Files

ATTRIBUTION.mdAdded by AutoGineer903 B
LICENSELicence file added by AutoGineer9.9 KiB
NOTICELicence file added by AutoGineer67 B
SKILL.md8.6 KiB
references/clients.md3.6 KiB
references/credentials.md3.4 KiB
references/dynamodb.md3.0 KiB
references/effective-practices.md2.3 KiB
references/error-handling.md1.6 KiB
references/lambda.md1.7 KiB
references/performance.md1.9 KiB
references/s3.md2.7 KiB
references/schemas.md1.7 KiB
references/sigv4a.md1.5 KiB
references/typescript.md1.1 KiB

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Requirements and compatibility

Works with: Claude Code, Claude apps, OpenAI Codex, GitHub Copilot, Cursor, Gemini CLI, Kiro, OpenCode, Goose, Amp, Roo Code, JetBrains Junie, Factory Droid, Devin (ex-Windsurf), Mistral Vibe, OpenHands, Letta

“Works with” means the tool reads the open Agent Skills format; a skill written for one tool may use features others lack.

Needs: Needs Node.js

Security

What our scanner noticed· Medium risk

References to credential files

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Attribution and licence

Published by

AWS

Publisher

AWS (Official)

Source

aws/agent-toolkit-for-aws · skills/core-skills/aws-sdk-js-v3-usage · commit 0a218f8

Licence

Apache License 2.0 (redistribution allowed)

LICENSE (added by AutoGineer from LICENSE)
NOTICE (added by AutoGineer from NOTICE)
ATTRIBUTION.md (written by AutoGineer)

Synced

2026-11-09

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