Cloud Technology and Services · Topic 10 of 11
Application Integration and Developer Tools
Learn SQS, SNS, EventBridge, Step Functions, API Gateway and the AWS Code services and X-Ray, and the difference between queues, topics and events.
- 4 min
- SQS is a queue that decouples components. SNS publishes one message to many subscribers.
- EventBridge routes events with rules and can run scheduled tasks.
- Step Functions orchestrates multi step workflows.
What it is
Applications built from many parts need a way to pass messages between them. Application integration services provide that glue, so the parts can work together without being tightly tied.
Developer tools cover the other side: building, testing and releasing the code. Together they support the loose coupling and automation ideas from the design principles page.
The exam asks you to tell the messaging services apart, and to match each developer tool to a step in the release process.
How it works
Messaging and events
| Service | Pattern | What it does |
|---|---|---|
| Amazon Simple Queue Service (SQS) | Queue | Holds messages until a consumer reads and processes them |
| Amazon Simple Notification Service (SNS) | Publish and subscribe | Sends one message to many subscribers, such as email, text messages or queues |
| Amazon EventBridge | Event bus | Routes events from AWS services, your apps and partners to targets using rules, and can run schedules |
| AWS Step Functions | Workflow | Coordinates several steps, such as Lambda functions, in a defined order |
| Amazon MQ | Message broker | Managed brokers for applications that already use ActiveMQ or RabbitMQ |
| Amazon API Gateway | Interface front door | Creates and publishes application programming interfaces (APIs) that clients can call |
SQS is a pull service, so the consumer asks the queue for messages when it is ready.
SNS is a push service. It delivers to all subscribers as soon as a message is published.
A queue protects the receiver from sudden spikes. If a burst of orders arrives, they wait in the queue and are handled at a steady pace.
Choosing between them
| Situation | Choose |
|---|---|
| Decouple two components and buffer work | SQS |
| Send the same message to many receivers | SNS |
| React to events from AWS services or run on a schedule | EventBridge |
| Run an ordered, multi step process with branches and retries | Step Functions |
| Offer a web interface in front of Lambda or other back ends | API Gateway |
Developer tools
These services form a delivery pipeline, often called CI/CD, which stands for continuous integration and continuous delivery.
| Service | Role |
|---|---|
| AWS CodeCommit | Hosts Git repositories for source code |
| AWS CodeBuild | Compiles code, runs tests and produces build outputs |
| AWS CodeDeploy | Deploys applications to Amazon Elastic Compute Cloud (EC2), Lambda or on premises servers |
| AWS CodePipeline | Automates the whole flow from commit to release |
| AWS CodeArtifact | Stores software packages and dependencies |
| AWS X-Ray | Traces requests through an application to find slow or failing parts |
CodePipeline sits on top and links the steps together, so each change moves through the stages in order.
Why this matters
Automating builds and releases makes deployments faster and less error prone. Tracing with X-Ray helps teams find the cause of slow responses in applications made of many services.
AWS also offers Amazon Q Developer, an assistant that helps developers write and understand code. It is part of the same developer tooling family.
What to remember for the exam
- SQS is a queue that decouples components. SNS publishes one message to many subscribers.
- EventBridge routes events with rules and can run scheduled tasks.
- Step Functions orchestrates multi step workflows.
- API Gateway creates and manages APIs.
- CodeBuild builds and tests, CodeDeploy deploys, and CodePipeline automates the whole flow.
- CodeCommit stores source code in Git repositories, and CodeArtifact stores packages.
- X-Ray traces requests to help debug distributed applications.
- Amazon MQ is for applications that already use standard brokers such as ActiveMQ or RabbitMQ.
"Queue" or "buffer" means SQS. "Fan out", "notify" or "subscribers" means SNS. "Orchestrate steps" means Step Functions.
Common mistakes
Mixing up SQS and SNS. SQS holds messages until a consumer pulls them, with each message handled by one consumer, while SNS pushes to many subscribers.
Using CodePipeline when only a build is needed. CodeBuild does the build and test, and CodePipeline links the stages.
Confusing X-Ray with CloudWatch. X-Ray traces individual requests across services. CloudWatch gathers metrics and logs.
Thinking EventBridge replaces SQS. EventBridge routes events by rule, while SQS provides a buffer.
SNS does not store messages for later pickup the way SQS does. A subscriber that is not available can miss a message unless it has a queue behind it.
Check yourself
Which service decouples components by holding messages in a queue?
Amazon SQS.
Which service sends one message to many subscribers?
Amazon SNS.
Which service automates the stages of a release from source to deployment?
AWS CodePipeline.
Topic 10 of 11 in Cloud Technology and Services
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