02. Amazon SQS (Simple Queue Service)
Amazon SQS (Simple Queue Service) is a fully managed message queuing service that allows you to decouple and scale microservices, distributed systems, and serverless applications.
When deploying multiple services, direct communication (App → App) can create tight coupling and scaling issues. SQS solves this by acting as a buffer between producers and consumers.
⚙️ How It Works
| Component | Role |
|---|---|
| Producer (Sender) | Sends messages to the SQS queue. Can be one or many producers. |
| Queue | Stores messages until they are processed or deleted. |
| Consumer (Receiver) | Polls (requests) messages from the queue and processes them. Can also be one or many consumers. |
✅ Multiple producers can send messages.
✅ Multiple consumers can process messages concurrently.
✅ Each message is delivered to only one consumer instance (point-to-point model).
🧱 Architecture Example
Scenario: A video-sharing platform where users upload videos for processing.
| Layer | Description |
|---|---|
| Frontend Web Servers | Accept user uploads and send “video processing” messages to SQS. |
| SQS Queue | Temporarily stores video processing requests. |
| Video Processing EC2 Group | Polls messages from SQS and encodes videos asynchronously. |
✅ Web and processing layers are decoupled
✅ Each can scale independently based on workload
✅ Processing layer can auto-scale based on queue length
⚡ Performance & Scaling
- Scales automatically from 1 to tens of thousands of messages per second.
- Low latency (< 10 ms for send/receive).
- No limit on queue size (unlimited messages).
- Message retention:
- Default: 4 days
- Maximum: 14 days
- Fully managed and serverless — no server provisioning required.
🧠 Exam Tips
| Feature | Description |
|---|---|
| Decoupling | Always think SQS when you see “decouple application tiers.” |
| Polling | Consumers poll the queue to receive messages. |
| Visibility Timeout | Prevents other consumers from processing a message that’s already being worked on. |
| Message Deletion | Must be deleted after successful processing. |
| FIFO Queues | Ensure message order (First-In-First-Out). |
🔁 SQS FIFO Queues
| Feature | Standard Queue | FIFO Queue |
|---|---|---|
| Order | Not guaranteed | Guaranteed |
| Throughput | Very high | Limited (but consistent) |
| Use Case | Parallel processing | Order-sensitive processing |
Example:
If messages are sent as 1 → 2 → 3 → 4,
a FIFO queue ensures consumers receive them in the same order.
🧠 Key Takeaway
Amazon SQS decouples your applications by introducing a message queue between producers and consumers.
It provides scalability, fault tolerance, and asynchronous processing — all fully managed by AWS.
SQS Hands On
Step 1: Create Queue
Step 2: Test Queue
