# Overview
* SNS is a managed service that **provides message delivery from publishers to subscribers (also known as producers and consumers)**.
* **Publishers communicate asynchronously with subscribers by sending messages to a topic**, which is a logical access point and communication channel.
* **Clients can subscribe to the SNS topic and receive published messages** using a supported protocol, such as **SQS, Lambda, HTTP, email, mobile push notifications, and mobile text messages (SMS)**.
* By default, SNS offers **10 million subscriptions per topic**, and **100,000 topics per account**.
* After you **create an SNS topic and subscribe an endpoint to it**, you can **publish messages to the topic**.\
* When a message is published, **SNS attempts to deliver the message to the subscribed endpoints**.
## Security
* Encryption in transit using HTTPS API.
* Encryption at rest using KMS.
* Access Controls using IAM Policies.
* Cross-account policies using SNS Access Policies.
---
# Agent Instructions: Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.
Perform an HTTP GET request on the current page URL with the `ask` query parameter:
```
GET https://karansingh.gitbook.io/aws-saa-c02/simple-notification-service-sns/overview.md?ask=
```
The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.
Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.