Event-Driven Architecture Modernization — AWS Developer (DVA-C02)
SQS Decouples. EventBridge Routes. The Topology Is Different.
An order service must notify inventory, billing, and shipping independently when an order is placed. Candidates reach for SQS because it decouples producers from consumers. SQS is point-to-point; multiple consumers compete for the same messages rather than each receiving their own copy. EventBridge routes a single event to multiple independent targets based on rules, with no consumer coordination required. DVA-C02 tests fan-out topology directly; decoupling as a general concept is not enough. SNS fan-out to SQS queues per consumer is a valid alternative when downstream consumers need independent retry and backlog management separate from each other.
What This Pattern Tests
The exam presents a tightly coupled system and asks how to decouple with events. SQS is for point-to-point: one producer, one consumer, messages buffered until processed (order processing, task queues). SNS is for fan-out: one event triggers multiple subscribers in parallel (email + SMS + Lambda). EventBridge is for content-based routing: events from 35+ AWS sources routed to targets based on event content (only route "order.placed" events to the billing service, "order.shipped" to the notification service). The trap is using SQS when multiple consumers need the same event (use SNS+SQS fan-out pattern) or EventBridge for simple point-to-point buffering (SQS is simpler and cheaper).
Decision Axis
Communication pattern determines the service: point-to-point buffering = SQS, parallel fan-out = SNS, content-based routing = EventBridge, fan-out with buffering = SNS+SQS.
Associated Traps
More Top Traps on This Exam
Decision Rules
When SQS is the event source (polling/event source mapping), DLQ ownership belongs to the SQS queue's redrive policy, not to the Lambda function's DLQ configuration, which is silent and ineffective for this invocation path.
Whether the root cause of DLQ accumulation is Lambda invocation errors (requiring exception investigation via CloudWatch Logs or X-Ray) versus Lambda throttling (requiring a concurrency increase), given that Throttles=0 categorically rules out the concurrency path.
Domain Coverage
Difficulty Breakdown