Start with the relationship
A service-selection problem is easier when the first sentence describes a relationship rather than a product. Does one producer need somewhere to leave work until a consumer is ready? Must every interested subscriber receive a notification? Do event attributes determine which target should respond? Must an execution remember which step completed before another step begins? These are related integration concerns, but they are not interchangeable. A design may use more than one of them. This lesson selects the capability that answers the stated requirement before adding a larger architecture.
Buffering work is a queue decision
Amazon SQS provides message queuing between application components. A queue lets a producer and a consumer operate at different rates: work can wait while a worker is busy or unavailable. The consumer still needs to process and acknowledge messages correctly. Standard queue delivery is at least once with best-effort ordering; the business operation should not assume that receiving a message proves a unique real-world action. Ordering and duplicate-handling requirements belong in the design explicitly. Do not infer that every order-processing example automatically requires a particular queue type.
Publication and routing answer different questions
Amazon SNS provides notification topics for push-based publication to subscribed endpoints. It supports application endpoints and end-user notifications such as email and SMS. Amazon EventBridge provides an event bus that connects event sources to targets through routing rules. Both can distribute information, and SNS also has filtering capabilities, so the word fan-out alone is not a universal discriminator. Look for the stated abstraction, integration sources and endpoint requirements. A problem naming an event bus with rules is different from one requiring a notification topic for email and SMS recipients.
Worked example: the repair desk
A fictional community repair desk records accepted repair requests. Its first gap is a backlog that available technicians can pull from, so a queue addresses that gap. It separately wants every subscribed coordinator to receive a new-request alert; that is a topic publication concern. Later, an equipment-change event should notify only a relevant regional handler according to event attributes; an event-bus rule addresses routing. These decisions can coexist. Selecting SQS for the backlog does not claim that all alerts, routing and workflows must also be implemented in the queue.
When an execution has several steps
AWS Step Functions coordinates components through state-machine workflows, including execution state and retry behavior. Suppose a booking must be validated before a reservation is attempted and a later confirmation depends on that result. Tracking the progression is a workflow concern. A topic delivers information to subscribers; an event bus selects targets; a queue buffers messages. None of those descriptions alone supplies the entire stated sequence with execution state. Conversely, a workflow should not be selected merely because an application has a sequence of events: identify whether managed coordination is actually required.
Transfer check and conditions
Change the repair desk into a public equipment register. A producer must keep accepting records while a worker is temporarily offline, and a separate monitoring subscriber should see every accepted-record alert. Explain the queue requirement and the publication requirement separately, then describe what additional condition would justify event-bus routing or a state-machine workflow. A defensible answer names the capability and the reason, without claiming that the alternatives cannot ever participate. Return to the requirement whenever two descriptions seem plausible: an event bus, notification topic, buffered backlog and tracked workflow are distinct architectural promises.
End-user delivery: desktop or application
Amazon WorkSpaces provides managed cloud desktops. Amazon WorkSpaces Applications provides managed application streaming, including delivering a centrally managed application without installing that application on the user’s local computer. A complete desktop and one streamed application are related end-user computing needs, but they have different delivery boundaries. A managed desktop service is also different from an organization operating its own desktop-host servers. Do not treat those choices as universally better or worse. State which experience must be delivered, who should operate the desktop hosts, and whether local application installation is allowed.
Worked comparison and transfer: a workshop
A fictional workshop has two groups. Staff need complete managed cloud desktops and do not want to run their own desktop-host servers; WorkSpaces directly matches that boundary. Visitors need only one centrally managed application on their existing computers without installing it; WorkSpaces Applications directly matches that narrower boundary. A full desktop might be capable of running the visitor application, but it is broader than the explicitly selected delivery model. Transfer: change the visitor requirement to a full assigned desktop. Explain which requirement changed and why the application-only proposal no longer supplies the whole requested environment. The check basis is the delivery and management boundary, not the presence of a familiar product name.
Email platform versus topic publication
Amazon SES is an email platform supporting messages using an organization’s addresses and domains, including transactional email. SNS topics address publication to subscribed notification endpoints, including email and SMS. A queue can buffer work before an application sends a message, but successful storage in a queue does not prove that a recipient received an email or SMS. This comparison names the direct responsibility instead of pretending every communication service is interchangeable. Operational sender identity, permissions, deliverability and recipient handling still need their own review; choosing a service purpose is not proof of completed delivery.
Worked email extension and transfer check
The workshop sends a registration receipt from its domain and separately alerts email/SMS subscribers when a session changes. SES matches the transactional email-platform purpose; SNS matches the subscriber-topic notification purpose. If the sender must tolerate a temporarily unavailable worker, a queue can address that additional backlog without replacing the actual notification stage. Transfer: an operator points to a successful queue write and claims that every subscriber has been notified. What is missing? The check basis is evidence for the actual consumer processing and notification delivery; storage success alone establishes only the earlier buffering stage.
Try it, then explain it.
Complete a short set without looking at the example. After each answer, explain which evidence or rule supports your decision and why the alternatives do not fit.
Sources & authorship
Original OpenExam explanations and examples. References support the concepts; they are not the source of copied questions. Independent educator review is pending.
rd-aws-desktopsrd-aws-integrationrd-aws-sesrd-aws-sns-filter