---
id: amazon-sns-extended-client
version: "1.0.1"
license: Apache-2.0
license_treatment: permissive
maintenance: dormant
---

# amazon-sns-extended-client — Python version of AWS SNS extended client to publish large payload message

License: permissive · Maintenance: dormant · Downloads: 158.5K/mo

## What it is and what it does

Amazon SNS Extended Client is a Python wrapper around boto3's SNS client that automatically handles messages too large for SNS's direct publish limit by storing them in S3 and sending only a reference through SNS. It mirrors the behavior of the Java library amazon-sns-java-extended-client-lib, allowing you to set a bucket name and optional size threshold on SNS client, Topic, or PlatformEndpoint objects, then publish normally—the library intercepts and routes large payloads to S3 transparently.

The package supports configurable thresholds (default 262144 bytes, minimum 0, maximum 262144), legacy message attributes for backward compatibility with older Java client versions, custom S3 clients with specialized configurations, and custom S3 keys via message attributes. It works with boto3's low-level SNS client, Topic resources, and PlatformEndpoint resources, and requires only that the target S3 bucket already exists and is accessible.

Use it for:

- Publishing messages larger than SNS's direct size limit (e.g., large JSON payloads, serialized objects) to SNS topics without manual chunking.
- Integrating SNS workflows with S3-backed storage when message size is unpredictable or occasionally exceeds SNS limits.
- Migrating from the Java SNS extended client library to Python while maintaining the same publish-and-reference pattern.
- Bridging legacy systems using the SQSLargePayloadSize attribute with newer systems using ExtendedPayloadSize.
- Controlling S3 upload behavior (region, signature version, accelerated endpoints) via custom boto3 S3 client configuration.

## Worth the install?

AI-flagged interpretation of the facts above — verify before relying.

Extends boto3's SNS client to publish messages larger than SNS's direct size limit by transparently storing them in S3 and sending a reference through SNS instead.

Yes, if you need to publish messages larger than SNS's direct limit and have S3 available. The library is stable (production classifier, latest release 2025-02-18), has low install friction (one dependency), and carries no known vulnerabilities. Maintenance is dormant but the codebase is small and the underlying AWS APIs are stable. Verify that your subscriber infrastructure can handle S3 reference resolution before deploying.

## Install

pip install amazon-sns-extended-client
uv add amazon-sns-extended-client
poetry add amazon-sns-extended-client

## Installing amazon-sns-extended-client

Before you install: Low friction: pure Python wheel with only boto3 as a runtime dependency. Latest release on 2025-02-18 with production/stable classifier, though maintenance is dormant—no active development but no red flags.

License in practice: Apache-2.0 permissive license allows commercial and private use with minimal restrictions; suitable for most production environments.

Quickstart:

pip install amazon-sns-extended-client

import boto3
from amazon_sns_extended_client import SNSExtendedClientSession

sns = boto3.client('sns')
sns.large_payload_support = 'my-bucket-name'
sns.publish(Message='large message content', TopicArn='arn:aws:sns:...')

S3 bucket must exist and be accessible with your AWS credentials before use; SNS topic must also exist.

Verify before relying:

- Whether message retrieval on the subscriber side (SQS, Lambda, etc.) requires additional client-side logic or if SNS/SQS handles S3 reference resolution automatically.
- Performance overhead and latency impact of S3 round-trip for messages near or above the threshold.
- Compatibility with SNS message filtering and other advanced SNS features when payloads are stored in S3.

## Package facts

- License: Apache-2.0 (permissive)
- Python support: supports_current
- Install friction: low
- Maintenance: dormant
- Downloads: 158.5K/month (top 15,000 on PyPI)
- Known vulnerabilities: none known

## Tags

SNS large message publishing, boto3 SNS extended payload, SNS S3 overflow handler, publish large messages to SNS, SNS message size limit workaround, AWS SNS extended client, SNS payload to S3 bridge, aws-integration, message-queue, s3-storage

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