What is Amazon SQS (Simple Queue Service)?

Amazon SQS is a fully managed message queuing service that enables decoupled, asynchronous communication between distributed application components. Messages are stored in a queue until a consumer retrieves and processes them, providing a reliable, scalable buffer between producers and consumers in microservices and event-driven architectures.

What is the difference between SQS Standard and FIFO queues?

SQS Standard Queue offers nearly unlimited throughput, at-least-once delivery, and best-effort ordering (messages may arrive out of order or be delivered more than once). SQS FIFO Queue guarantees exactly-once processing and strict ordering (First-In, First-Out) — ideal for financial transactions, order processing, and workflows requiring strict message ordering.

How does SQS visibility timeout work?

When a consumer reads a message from SQS, the message becomes invisible to other consumers for the Visibility Timeout period (default 30 seconds). If the consumer successfully processes and deletes the message within this window, it's permanently removed. If not (e.g., consumer crashes), the message becomes visible again for reprocessing after the timeout expires.

What is a Dead Letter Queue (DLQ) in Amazon SQS?

A Dead Letter Queue (DLQ) is a secondary SQS queue where messages are automatically redirected after failing to be processed successfully a maximum number of times (configured via maxReceiveCount). DLQs enable you to isolate, analyse, and remediate problematic messages without affecting the main queue's processing.

Amazon SQS Deep Dive: Features, Queue Types & Pricing Guide

March 9, 2021 / Nirav Shah

Deep Dive into Amazon Simple Queue Service (SQS): Complete Guide

What Is Amazon Simple Queue Service (SQS)?

SQS is a Polling service in AWS.
SQS is fast, reliable and fully managed message queue service.
It is a web service that gives you access to a message queue that store message waiting to be processed.
It offers a reliable, highly scalable hosted queue for storing message between server.
It allows the decoupling of application components such that a failure in one component does not cause a bigger problem to application functionality.
Using SQS, you can no longer need a highly available message cluster or the burden of running it.
You can delete all messages in SQS without deleting the SQS queue itself.
You can use an application on EC2 instance to read and process the SQS queue message.
The application on EC2 instance can process the SQS message than post the results to other SQS queue or other AWS Service.

AWS SQS Queue Types: Standard Queue vs FIFO Queue

Standard Queue	FIFO queue
High or unlimited throughput At least one delivery Duplicity is not possible Best offer ordering	Limited throughput Exactly one processing Duplicity is possible First in first out ordering

As we know SQS is polling services from AWS.

There are two types of pulling.

Short polling – A request returns immediately even if a queue is empty and it does not wait for the message to appear in the queue.

Long polling – long-polling does not return a response until a message arrives in the message queue.

Amazon SQS Pricing: How Much Does It Cost?

Billing is based on the API request. The first 1 million monthly requests are free. After that pricing is accordingly to the region which is mentioned at the official AWS page. For example, In Mumbai region

Standard Queue – $0.40/million request
FIFO Queue – $0.50/million request

With this information, you can decide and use as per the requisite volume.

FAQs:

1.Can SNS send message to SQS?

2.How many SQS queues can I have?

3.What is the difference between Amazon MQ and SQS?

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Nirav Shah

Nirav Shah is the Director of Eternal Web Pvt Ltd, an AWS Advanced Consulting Partner and certified Odoo Partner based in the UK. With over a decade of experience in cloud computing, digital transformation, and ERP implementation, Nirav helps enterprises adopt the right technology to solve complex business challenges. He specialises in AWS infrastructure, Odoo ERP, and web development solutions for businesses across the UK and beyond.