Amazon SQS

Amazon Simple Queue Service (SQS) is a fully managed message queuing service that enables decoupling and scaling of microservices, distributed systems, and serverless applications.

Queue Types

Type	Throughput	Ordering	Deduplication
Standard	Unlimited	Best-effort	At-least-once
FIFO	3,000 msg/s	Guaranteed	Exactly-once

Key Concepts

• Messages: Up to 256 KB of text data
• Visibility timeout: Time a message is hidden after being read
• Dead-letter queue: Destination for messages that can't be processed
• Long polling: Reduce empty responses and costs

Common Patterns

Decoupling Services

Web Server → SQS → Worker → Database

Load Leveling

Handle traffic spikes by queuing work for steady processing.

Fan-out with SNS

SNS Topic → [SQS Queue 1, SQS Queue 2]

Each queue processes independently.

Example: Processing Messages

const sqs = new AWS.SQS();

// Send
await sqs.sendMessage({
  QueueUrl: 'https://sqs.us-east-1.amazonaws.com/123456789/my-queue',
  MessageBody: JSON.stringify({ task: 'process_order', orderId: '12345' })
}).promise();

// Receive
const { Messages } = await sqs.receiveMessage({
  QueueUrl: 'https://sqs.us-east-1.amazonaws.com/123456789/my-queue',
  MaxNumberOfMessages: 10,
  WaitTimeSeconds: 20  // Long polling
}).promise();

What We Like

• Reliability: Messages are stored redundantly across multiple AZs
• Scalability: Handles any volume without configuration
• Cost: Pay only for what you use, no minimum fees
• Lambda integration: Native trigger support for serverless processing

What We Don't Like

• 256 KB limit: Large payloads need S3 integration (Extended Client Library)
• Visibility timeout complexity: Requires careful tuning
• No message filtering: All consumers receive all messages (use SNS + SQS for filtering)
• FIFO limitations: Lower throughput, regional restrictions

Best Practices

1. Use long polling to reduce costs and empty responses
2. Set appropriate visibility timeouts based on processing time
3. Configure dead-letter queues for failed message handling
4. Use FIFO queues only when ordering is critical
5. Enable server-side encryption for sensitive data