AWS SNS Interview Questions and Answers

AWS Interview Questions and Answers

What is Amazon SNS and how does it work?

Amazon SNS (Simple Notification Service) is a fully-managed messaging service provided by AWS (Amazon Web Services) that enables applications, services, and devices to send and receive notifications from the cloud. SNS supports a variety of messaging protocols and transports, such as HTTP/HTTPS, email, SMS, mobile push notifications, and Amazon SQS (Simple Queue Service).

SNS works by providing a publish-subscribe model, where applications and services can publish messages to SNS topics, and subscribers can receive these messages through their preferred protocol or transport. When a message is published on a topic, SNS delivers a copy of the message to each of the subscribers that have subscribed to the topic.

To use SNS, you first create a topic, which represents a logical access point for subscribers to receive messages. You can then subscribe endpoints, such as email addresses, phone numbers, HTTP/HTTPS endpoints, or mobile devices, to the topic. When a message is published to the topic, SNS sends the message to all the subscribed endpoints.

SNS also provides features such as message filtering, message delivery retries, and dead-letter queues to enhance message delivery and reliability. Additionally, SNS can be integrated with other AWS services, such as AWS Lambda, Amazon SQS, and Amazon S3, to enable advanced use cases such as serverless application architectures and real-time data processing.

Overall, SNS simplifies the process of sending and receiving messages between distributed systems, services, and applications, making it a powerful tool for building scalable, resilient, and event-driven architectures in the cloud.

What are the benefits of using Amazon SNS?

There are several benefits of using Amazon SNS:

Scalability: SNS is a fully managed service that can scale automatically to handle large volumes of messages, ensuring high availability and performance.
Flexibility: SNS supports a wide range of messaging protocols and transports, such as HTTP/HTTPS, email, SMS, mobile push notifications, and Amazon SQS. This enables developers to use the same messaging service for various use cases and platforms.
Cost-effectiveness: SNS follows a pay-as-you-go pricing model, which means you only pay for the messages you send and receive. This makes it cost-effective for small as well as large-scale deployments.
Easy integration: SNS integrates easily with other AWS services, such as AWS Lambda, Amazon SQS, and Amazon S3, enabling you to build advanced event-driven architectures and real-time data processing pipelines.
Reliability: SNS provides features such as message filtering, message delivery retries, and dead-letter queues to enhance message delivery and reliability.
Security: SNS supports various security features such as encryption, access control, and identity and access management, ensuring that messages are delivered securely to the intended recipients.

Overall, Amazon SNS simplifies the process of sending and receiving messages between distributed systems, services, and applications, making it a powerful tool for building scalable, resilient, and event-driven architectures in the cloud.

What are the different types of endpoints that can be subscribed to an SNS topic?

Amazon SNS supports a variety of endpoints that can be subscribed to a topic, including:

HTTP/HTTPS endpoints: These are web endpoints that can receive messages over HTTP/HTTPS. The endpoint can be an Amazon EC2 instance, a web server, or any other web-based application.
Email endpoints: These are email addresses that can receive messages in the form of emails.
SMS endpoints: These are phone numbers that can receive messages in the form of SMS messages.
Mobile push endpoints: These are mobile devices that can receive messages in the form of push notifications. SNS supports various mobile platforms, including iOS, Android, Fire OS, and Windows.
Lambda function endpoints: These are AWS Lambda functions that can receive messages as input events. This allows you to build serverless architectures that can react to events in real time.
Amazon SQS endpoints: These are Amazon SQS queues that can receive messages as notifications. This enables you to build distributed systems that can handle high volumes of messages.

Overall, SNS provides a flexible and scalable platform for sending messages to a wide range of endpoints, making it easy to build event-driven architectures and real-time data processing pipelines.

What is the maximum size of a message that can be published to an SNS topic?

The maximum size of a message that can be published to an SNS topic depends on the protocol used to send the message. Here are the maximum message sizes for different protocols:

HTTP/S and email: 256 KB
SMS: 160 characters for ASCII messages or 70 characters for non-ASCII messages
Mobile push notifications: 2 KB for most platforms, except for APNS (Apple Push Notification Service) which has a limit of 4 KB
Lambda function: 256 KB
Amazon SQS: 256 KB

It’s important to note that when publishing messages to SNS, you should always consider the maximum message size for the protocol you are using to ensure that your messages are delivered successfully. If you need to send larger messages, you can use techniques such as message fragmentation, compression, or storing the message payload in an external data store and sending a reference to it in the message.

How can you publish messages to an SNS topic?

You can publish messages to an SNS topic using the AWS Management Console, AWS SDKs, or the AWS Command Line Interface (CLI). Here are the general steps:

Create an SNS topic: If you haven’t already created an SNS topic, you can create one using the AWS Management Console or the AWS CLI.
Create an endpoint: You’ll need to create an endpoint for each subscriber that you want to receive the message. This could be an email address, phone number, HTTP/HTTPS endpoint, mobile push endpoint, Lambda function, or Amazon SQS queue.
Subscribe endpoints to the topic: Once you’ve created the endpoints, you’ll need to subscribe them to the topic using the AWS Management Console, SDKs, or CLI.
Publish a message: To publish a message to the topic, you’ll need to call the SNS Publish API with the message payload and the ARN (Amazon Resource Name) of the topic.

Here’s an example of how to publish a message to an SNS topic using the AWS CLI:

aws sns publish –topic-arn arn:aws:sns:us-west-2:123456789012:my-topic –message “Hello world!”

This command publishes the message “Hello world!” to the SNS topic with the ARN arn:aws:sns:us-west-2:123456789012:my-topic.

Note that you can also include optional parameters, such as the message structure, message attributes, and message subject.

What is a subscription filter policy in SNS?

A subscription filter policy in SNS is a JSON policy that allows subscribers to filter the messages they receive from a topic based on message attributes. When you create a subscription, you can specify a filter policy that includes a set of attribute names and values. Only messages that match the specified attributes will be delivered to the subscriber.

Here’s an example of a subscription filter policy:

{

“price”: [{“numeric”: [“>=”, 10]}, {“numeric”: [“<=”, 100]}],

“color”: [“red”, “blue”]

}

This policy includes two attributes: price and color. The price attribute must be a numeric value between 10 and 100, while the color attribute must be either “red” or “blue”. If a message includes both of these attributes and they meet the specified conditions, the message will be delivered to the subscriber. If a message doesn’t include one of these attributes, or if the attribute value doesn’t meet the specified conditions, the message will be discarded.

Subscription filter policies can help reduce unnecessary message delivery and processing costs, as well as improve security and compliance by allowing subscribers to receive only the messages they are interested in.

What are the different types of subscription endpoints that SNS supports?

SNS supports several types of subscription endpoints, which allow subscribers to receive messages in different ways. Here are some of the most common types:

Email: Subscribers can receive messages via email. When a message is published to an SNS topic, it’s sent to the subscriber’s email address as a formatted email message.
SMS: Subscribers can receive messages via SMS. When a message is published to an SNS topic, it’s sent to the subscriber’s phone number as a text message.
HTTP/HTTPS: Subscribers can receive messages via HTTP/HTTPS endpoints. When a message is published to an SNS topic, it’s sent as an HTTP POST or HTTPS POST request to the subscriber’s endpoint.
Mobile push notifications: Subscribers can receive messages as mobile push notifications. SNS supports several mobile platforms, including Apple Push Notification Service (APNS), Google Cloud Messaging (GCM), Firebase Cloud Messaging (FCM), and Amazon Device Messaging (ADM).
Lambda function: Subscribers can receive messages by invoking an AWS Lambda function. When a message is published to an SNS topic, it triggers the Lambda function, which can then process the message or perform any other desired action.
Amazon SQS queue: Subscribers can receive messages by sending them to an Amazon Simple Queue Service (SQS) queue. When a message is published to an SNS topic, it’s automatically sent to the specified SQS queue.

These different types of subscription endpoints allow subscribers to receive messages in different ways, depending on their needs and preferences.

Can you use SNS to send messages to mobile devices?

Yes, SNS can be used to send messages to mobile devices. SNS supports mobile push notifications for several platforms, including Apple Push Notification Service (APNS), Google Cloud Messaging (GCM), Firebase Cloud Messaging (FCM), and Amazon Device Messaging (ADM).

To send push notifications to mobile devices, you first need to create an SNS platform application for the desired platform. This involves registering your application with the platform provider and obtaining the necessary credentials and configuration settings.

Once you have created an SNS platform application, you can publish messages to the associated SNS topic, which will then be sent to the mobile devices registered with the application. The message format and content depend on the specific platform and application configuration.

SNS also supports mobile text messaging (SMS) for sending messages to mobile devices that don’t support push notifications or when push notifications are not preferred.

What is the difference between an SNS topic and an SQS queue?

SNS topics and SQS queues are both messaging services provided by AWS, but they serve different purposes and have different characteristics.

An SNS topic is a pub/sub-messaging service that allows publishers to send messages to multiple subscribers at once. When a message is published to an SNS topic, it’s sent to all subscribers that have subscribed to that topic. Subscribers can receive the message in various ways, such as email, SMS, mobile push notification, HTTP/HTTPS endpoint, Lambda function, or SQS queue.

On the other hand, an SQS queue is a messaging service that allows messages to be stored and retrieved by consumers. When a message is sent to an SQS queue, it’s stored in the queue until a consumer retrieves it. Consumers can retrieve messages from the queue and process them in any desired way, such as sending an email, updating a database, or triggering a Lambda function.

Here are some key differences between SNS topics and SQS queues:

Message distribution: SNS topics allow messages to be distributed to multiple subscribers, while SQS queues allow messages to be consumed by a single consumer.
Message persistence: SNS topics do not persist messages, meaning that if a subscriber is not available to receive a message, the message is lost. SQS queues persist messages until a consumer retrieves them, ensuring that messages are not lost if a consumer is temporarily unavailable.
Message ordering: SNS topics do not preserve message ordering, meaning that messages may not be delivered to subscribers in the order they were sent. SQS queues preserve message ordering, ensuring that messages are consumed in the order they were sent.
Message retrieval: SNS topics do not provide a way to retrieve past messages, while SQS queues allow consumers to retrieve messages that were sent in the past.

In summary, SNS topics are best suited for pub/sub messaging scenarios where multiple subscribers need to receive the same message simultaneously, while SQS queues are best suited for message queuing scenarios where messages need to be stored and processed by a single consumer.

Can an SNS topic be used to send messages to an AWS Lambda function?

Yes, an SNS topic can be used to send messages to an AWS Lambda function. When a Lambda function is subscribed to an SNS topic, it receives messages as events and can process them in real-time. This allows SNS to trigger Lambda functions in response to various events, such as incoming data or changes in a database.

To subscribe a Lambda function to an SNS topic, you first need to create the Lambda function and the SNS topic. Then, you can use the AWS Management Console, AWS CLI, or AWS SDK to configure the subscription. Here are the general steps:

Create a Lambda function: Create a Lambda function that will process the SNS messages. You can use the AWS Management Console or AWS CLI to create a Lambda function.
Create an SNS topic: Create an SNS topic that will be used to send messages to the Lambda function. You can use the AWS Management Console or AWS CLI to create an SNS topic.
Subscribe the Lambda function to the SNS topic: Use the AWS Management Console, AWS CLI, or AWS SDK to subscribe the Lambda function to the SNS topic. When you subscribe the Lambda function to the SNS topic, you specify the ARN of the Lambda function.
Publish messages to the SNS topic: Use the AWS Management Console, AWS CLI, or AWS SDK to publish messages to the SNS topic. When a message is published to the SNS topic, it triggers the Lambda function, which processes the message.

Overall, using SNS to trigger Lambda functions is a powerful way to build event-driven applications in AWS.

What is the difference between an SNS topic and an SNS queue?

There is no such thing as an “SNS queue”. SNS (Simple Notification Service) is a publish-subscribe messaging service that allows messages to be sent to multiple subscribers (endpoints) at once. It uses topics to organize messages and subscriptions to specify the endpoints that receive the messages.

On the other hand, SQS (Simple Queue Service) is a message queuing service that allows messages to be sent between applications and distributed systems. It uses queues to store messages until they are consumed by a consumer application or system.

The key difference between SNS and SQS is that SNS is designed for fan-out (broadcast) messaging to multiple subscribers, whereas SQS is designed for point-to-point messaging between a single producer and consumer.

In summary, SNS is a publish-subscribe messaging service that uses topics and subscriptions, while SQS is a message queuing service that uses queues.

Can you encrypt messages sent through SNS?

Yes, you can encrypt messages sent through SNS (Simple Notification Service) using AWS Key Management Service (KMS). SNS allows you to specify a customer-managed KMS key to encrypt the messages published to the topic. This provides an additional layer of security to ensure that the messages are only readable by authorized parties.

To encrypt messages sent through SNS, you first need to create a customer-managed KMS key in AWS KMS. Then, you can configure the SNS topic to use the KMS key for message encryption. Here are the general steps:

Create a customer-managed KMS key: Use the AWS Management Console or AWS CLI to create a customer-managed KMS key in AWS KMS.
Configure the SNS topic to use the KMS key: Use the AWS Management Console or AWS CLI to configure the SNS topic to use the KMS key for message encryption. When you create or update the SNS topic, you specify the ARN of the KMS key.
Publish messages to the encrypted SNS topic: Use the AWS Management Console, AWS CLI, or AWS SDK to publish messages to the encrypted SNS topic. The messages will be automatically encrypted with the specified KMS key.

Overall, encrypting messages sent through SNS using AWS KMS provides an additional layer of security to ensure that the messages are only readable by authorized parties.

How does SNS handle message delivery failures?

When a message is published to an SNS (Simple Notification Service) topic, SNS attempts to deliver the message to all subscribed endpoints. However, delivery failures can occur due to various reasons such as network issues, permission errors, or endpoint failures.

SNS provides several mechanisms to handle message delivery failures:

Retry: SNS automatically retries message delivery multiple times for a configurable period before marking the message as failed. The default number of retries is three, and the retry interval increases exponentially with each retry. You can configure the retry behavior using the “Delivery Retry Policy” setting when creating an SNS topic.
Dead-letter queue: SNS supports sending failed messages to a dead-letter queue (DLQ) for further analysis or processing. You can configure a DLQ for an SNS topic to receive messages that could not be delivered to the subscribed endpoints. This allows you to monitor and troubleshoot message delivery failures.
Monitoring and alerts: SNS integrates with Amazon CloudWatch to provide metrics and logs for monitoring the message delivery status. You can set up CloudWatch alarms to receive notifications when delivery failures exceed a certain threshold.
Redrive policy: When configuring a DLQ for an SNS topic, you can also set up a redrive policy to specify the number of times a message can be retried from the DLQ before it is discarded. This allows you to control the number of times a failed message is retried.

Overall, SNS provides various mechanisms to handle message delivery failures, including retry, dead-letter queue, monitoring and alerts, and redrive policy. This ensures that messages are reliably delivered to their intended endpoints, even in the case of delivery failures.

What is the maximum number of subscribers that an SNS topic can have?

Amazon SNS (Simple Notification Service) does not impose a hard limit on the number of subscribers that can be attached to a single topic. However, there are some practical limits that you should be aware of:

Rate limits: SNS limits the rate at which messages can be delivered to endpoints to prevent overloading and protect against denial-of-service attacks. The maximum rate depends on the type of endpoint and the region, and it can be increased by requesting a limit increase.
Endpoint capacity: The maximum number of subscribers that an SNS topic can support depends on the capacity of the subscribed endpoints. For example, if you have a topic that sends messages to an email address, the maximum number of subscribers will be limited by the capacity of the email service to receive and process messages.
Available resources: The number of subscribers that an SNS topic can support may also depend on the available resources, such as memory and network bandwidth, of the underlying infrastructure.

In general, SNS is designed to scale to support a large number of subscribers, and you should be able to attach thousands of subscribers to a single topic without any issues. If you need to support an even larger number of subscribers, you can consider using SNS Fanout, which allows you to distribute messages to multiple topics and subscribers in parallel.

How can you monitor SNS activity and performance?

You can monitor the activity and performance of Amazon SNS (Simple Notification Service) using several tools and features provided by AWS. Here are some ways to monitor SNS:

AWS CloudWatch: SNS publishes several metrics to CloudWatch, which you can use to monitor the health and performance of your SNS topics, including message delivery rates, success and failure rates, and message latency.
SNS Delivery Status: SNS provides delivery status logs that show the delivery status of every message sent to a topic, including whether it was delivered, failed, or retried. You can use these logs to troubleshoot delivery issues and monitor the overall health of your SNS topics.
SNS Mobile Analytics: If you’re using SNS to send mobile push notifications, you can use Amazon Mobile Analytics to track metrics such as the number of notifications sent, received, and opened, as well as user engagement and retention.
SNS Event Delivery: SNS supports integration with AWS Lambda, which allows you to trigger Lambda functions in response to SNS messages. You can use Lambda to process SNS events and perform custom monitoring and logging.
SNS CloudTrail: SNS is integrated with AWS CloudTrail, which provides a record of all SNS API calls and events. You can use CloudTrail to audit SNS activity and monitor changes to SNS resources and configurations.

Overall, monitoring SNS activity and performance is critical for ensuring that your notifications are delivered reliably and efficiently. By using the tools and features provided by AWS, you can gain visibility into your SNS topics and quickly identify and resolve any issues that arise.

Can you use SNS to send messages to a non-AWS endpoint?

Yes, you can use Amazon SNS (Simple Notification Service) to send messages to non-AWS endpoints, such as mobile devices, email addresses, and SMS text messaging services.

To do this, you need to create an SNS topic and then create a subscription for the non-AWS endpoint. For example, if you want to send a message to a mobile device, you can create an SNS topic and then create a subscription for the mobile device’s push notification service (such as Apple Push Notification Service or Google Cloud Messaging).

Once the subscription is created, you can publish messages to the SNS topic, and they will be delivered to the subscribed non-AWS endpoint. Note that some non-AWS endpoints may require additional configuration or authentication to receive messages from SNS.

Overall, SNS provides a flexible and scalable way to send messages to a wide range of endpoints, whether they are within or outside of the AWS ecosystem.

How can you restrict access to an SNS topic?

Access to an SNS (Simple Notification Service) topic can be restricted by using AWS Identity and Access Management (IAM) policies. IAM allows you to control access to your AWS resources, including SNS topics.

You can create IAM policies that specify which AWS users or roles have permission to perform specific actions on an SNS topic. For example, you can create a policy that grants only specific users or roles permission to publish messages to a particular SNS topic.

To restrict access to an SNS topic using IAM:

Create an IAM policy that specifies the permissions you want to grant or restrict.
Attach the policy to an IAM user or role.
Ensure that the user or role has the necessary permissions to perform the actions specified in the policy.
Test the policy to ensure that it works as expected.

By using IAM policies to control access to SNS topics, you can ensure that only authorized users or applications can interact with your SNS topics.

How does SNS ensure message delivery order?

By default, SNS (Simple Notification Service) doesn’t guarantee the order in which messages are delivered to subscribers. However, SNS does provide a way to enforce ordering through the use of message grouping.

When messages are published to an SNS topic, they can be assigned a message group ID. Messages that have the same group ID are guaranteed to be delivered to subscribers in the order in which they were published. This ensures that messages with the same group ID are processed in the order in which they were received by SNS.

Note that messages with different group IDs are not guaranteed to be delivered in any particular order, and SNS may deliver them out of order.

To use message grouping in SNS, you must specify a message group ID when publishing messages to the topic. You can do this using the message attributes parameter when calling the Publish API. Subscribers can then use the message group ID to process messages in the correct order.

It’s important to note that using message grouping may affect the performance of your SNS topic, as SNS must manage the order of messages within each group. Additionally, message grouping is not supported for all SNS subscribers, so you should check the documentation for each subscriber type to determine if message grouping is supported.

How can you configure message filtering in SNS?

To configure message filtering in SNS (Simple Notification Service), you can use subscription filter policies. A filter policy is a JSON document that specifies the types of messages that a subscriber is interested in receiving from a topic.

When you subscribe an endpoint to an SNS topic, you can specify a filter policy. The filter policy allows you to select only the messages that meet the criteria you define. SNS evaluates the filter policy for each message published to the topic, and delivers the message only to the endpoints that have a matching subscription.

Here are the steps to configure message filtering in SNS:

Create an SNS topic, or choose an existing one.
Create one or more subscriptions to the topic, specifying the subscription protocol and endpoint.
Specify a filter policy when creating or modifying the subscription. The filter policy is a JSON document that defines the criteria for messages that the subscriber is interested in.
Publish messages to the SNS topic, ensuring that the messages have the appropriate attributes that match the filter policy.
SNS will evaluate the filter policy for each message and deliver the message only to the subscribers that have a matching subscription.

You can use various attributes to create filter policies, including message attributes, message structure, and metadata. For example, you could create a filter policy that only delivers messages to subscribers that have subscribed to a specific topic and have requested messages with a specific attribute value.

Note that message filtering is not supported for all SNS subscribers, so you should check the documentation for each subscriber type to determine if message filtering is supported.

Can you use SNS to send messages between AWS accounts?

Yes, you can use SNS to send messages between AWS accounts. To do this, you would need to configure cross-account access by creating an IAM role in the receiving account that allows access to the SNS topic in the sending account.

The IAM role would need to include permissions to subscribe to the SNS topic and access any other AWS resources needed to process the messages, such as Lambda functions or SQS queues.

Once the IAM role is created, the sending account would need to grant permission to the role to subscribe to the SNS topic. This can be done by adding a statement to the SNS topic policy that allows the IAM role to subscribe to the topic.

After the permissions are set up, messages can be sent from the sending account to the SNS topic, and they will be delivered to the IAM role in the receiving account. The IAM role can then process the messages and take any necessary actions.

How can you set up email notifications with SNS?

To set up email notifications with SNS, follow these steps:

Open the Amazon SNS console and create a new topic if you haven’t already done so.
In the SNS console, click on the “Subscriptions” tab for the topic and then click the “Create subscription” button.
Select the “Email” protocol and enter the email address where you want to receive notifications.
Confirm the subscription by clicking the link in the confirmation email that is sent to the email address.
Once the subscription is confirmed, you can publish messages to the SNS topic, and they will be sent to the subscribed email address.

Note that you can also set up email notifications using the AWS Command Line Interface (CLI) or SDKs. Additionally, you can customize the email message that is sent by creating a subscription filter policy for the topic. This allows you to filter messages based on their attributes and only send notifications for messages that meet certain criteria.

Can you use SNS to trigger AWS Lambda functions?

Yes, you can use SNS to trigger AWS Lambda functions. To do this, you need to create an SNS topic and subscribe to the Lambda function to the topic. When a message is published on the topic, SNS will deliver the message to the Lambda function.

Here are the high-level steps to set up SNS to trigger a Lambda function:

Create an SNS topic in the Amazon SNS console.
Create a Lambda function in the AWS Lambda console.
In the Lambda function configuration, under “Triggers,” click the “Add trigger” button and select “SNS.”
Choose the SNS topic you created in step 1 and configure the trigger settings.
Save the Lambda function configuration.
Publish a message to the SNS topic using the SNS console or API.
SNS will deliver the message to the Lambda function, which will execute the function code.

Note that you can also use SNS to trigger Lambda functions written in other programming languages, as long as they are supported by Lambda.

How can you use SNS to send messages to HTTP/HTTPS endpoints?

Yes, you can use Amazon SNS to send messages to HTTP/HTTPS endpoints. This is achieved through the use of an HTTP/HTTPS subscription endpoint, which is a URL that SNS can use to send HTTP/HTTPS POST requests with message data.

To set up an HTTP/HTTPS subscription endpoint for an SNS topic, you can follow these steps:

Create an HTTP/HTTPS endpoint that can receive POST requests from SNS. This endpoint could be a web server, an AWS Lambda function, or any other HTTP/HTTPS endpoint that can receive and process POST requests.
Subscribe the endpoint to an SNS topic by creating a subscription request. This can be done either through the AWS Management Console or through the AWS SDK.
Confirm the subscription request by responding to the confirmation message sent by SNS. This confirmation ensures that the endpoint owner has authorized the subscription to the topic.

Once the subscription is confirmed, SNS can send messages to the HTTP/HTTPS endpoint by making a POST request to the endpoint URL with the message data included in the request body. The endpoint can then process the message data as needed.

Can you use SNS to send messages to Amazon Kinesis?

Yes, SNS can be used to send messages to Amazon Kinesis streams. To do this, you can create an SNS topic and subscribe an Amazon Kinesis stream to the topic. When a message is published to the topic, it will be delivered to the subscribed Kinesis stream as a record. This can be useful for scenarios where you want to process real-time data streams using Kinesis, and you want to trigger the processing based on events or messages published to an SNS topic.

What is SNS FIFO and how does it differ from SNS standard?

SNS FIFO (First-In-First-Out) is a messaging mode for Amazon SNS that provides strict message ordering and deduplication. It is designed for use cases where the order of messages is critical, such as in financial transactions, stock trading, or any application that requires a deterministic order of processing.

SNS FIFO differs from the standard SNS messaging mode in several ways. First, SNS FIFO guarantees that messages are delivered in the order they are sent, whereas the standard mode does not make this guarantee. Second, SNS FIFO provides deduplication, meaning that it ensures that a message is delivered only once to each subscriber, even if it is published multiple times. Finally, SNS FIFO supports a limited set of subscription types compared to the standard mode.

To use SNS FIFO, you must create a FIFO topic, which has a name that ends with “.fifo”. You can then publish messages to the topic, specifying a message group ID to ensure that messages are delivered in the order they are sent. You can also set a message deduplication ID to ensure that messages are not delivered more than once.

Note that SNS FIFO is a more expensive option compared to the standard mode due to the added features and capabilities it provides.

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