AWS SQS - Reliable Messaging Between Services

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Arjit Sharma
02 Mins

When your services need to talk without depending on each other in real time, we would need a message queue that decouples components and keeps your app resilient.

What Is SQS?

AWS SQS is a fully managed message queue service that enables you to send, store, and receive messages between distributed parts of your system (safely and asynchronously)

When to Use SQS:

  • Decouple microservices or distributed systems
  • A component might be slow or unavailable, but you still want to keep sending messages
  • Store messages temporarily in case of processing delays

How SQS Works

  • A producer sends a message to an SQS queue.
  • A consumer reads messages from the queue and processes them.
  • Messages stay in the queue until they’re processed or expire.

Key Concepts in SQS (At a Glance)

ConceptDescription
QueueA storage mechanism for messages waiting to be processed.
MessageThe content sent to the queue by producers.
Visibility TimeoutThe time a message is hidden after being read by a consumer to avoid duplication.
Dead Letter Queue (DLQ)A queue for messages that can’t be processed successfully.
Long PollingA mechanism for reducing empty responses when polling a queue.

Example - Using SQS to Handle User Registrations Asynchronously

Let’s say you want to decouple your user signup process so your app remains fast, even if downstream processing (like sending a welcome email) is slow.

Here’s how to do it using SQS + Lambda

Step 1: Create a Queue

  • Go to SQS → Create Queue.
  • Choose a Standard queue.
  • Give it a name

Step 2: Send a Message on Signup

In your application backend (e.g., Node.js), send a message to SQS using the AWS SDK.

const AWS = require('aws-sdk');
const sqs = new AWS.SQS();

const sendSignupMessage = async (user) => {
  const params = {
    QueueUrl: process.env.QUEUE_URL, // e.g., from env vars or AWS Console
    MessageBody: JSON.stringify({
      username: user.username,
      email: user.email,
    }),
  };

  await sqs.sendMessage(params).promise();
};

Call sendSignupMessage() when a new user signs up.

Step 3: Process Messages with Lambda

Set up a Lambda function triggered by the queue to process user data:

exports.handler = async (event) => {
  for (const record of event.Records) {
    const user = JSON.parse(record.body);
    // Process user registration (e.g., send email)
    console.log(`New user: ${user.username} (${user.email})`);
  }
};
  • Connect this Lambda to your SQS queue under Event Source Mapping.
  • SQS will invoke the Lambda whenever a new message arrives.
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