Event-Driven Architecture: EventBridge and Step Functions#

Queues move messages; events announce that something happened. The exam tests whether you can pick between “process this work item” (SQS), “notify everyone” (SNS), “route this event” (EventBridge) and “orchestrate this workflow” (Step Functions).

Amazon EventBridge#

The evolution of CloudWatch Events: a serverless event bus with rules.

Default bus - AWS service events (EC2 (Elastic Compute Cloud) state changes, S3 (Simple Storage Service) events via CloudTrail…)
Custom bus - your application’s events; can be shared cross-account
Partner sources - SaaS events (Zendesk, Datadog, Shopify…) land directly in your bus
Rules match event patterns and route to targets (Lambda, SQS, SNS, Step Functions…)
Content filtering: event patterns filter on fields before delivery (unlike SNS which delivers everything)
Archive and replay - store events and replay them later (“we lost 2 hours of processing”)
Schema registry - discover and generate code for event shapes

Need	Answer
Durable work queue, backpressure	SQS
One message → many push subscribers	SNS
Filter and route events by content, multiple sources, replay	EventBridge
Fan-out with durability	SNS → SQS (or EventBridge → SQS)

“Event pattern filtering” and “replay archived events” are the two keywords that make EventBridge the answer.

AWS Step Functions#

Serverless workflow orchestration - each step is a state, defined in JSON (Amazon States Language).

Integrates natively with Lambda, ECS (Elastic Container Service), SQS, DynamoDB, and 200+ services
Built-in retries, error handling, timeouts, wait states, parallel branches
Standard workflows - long-running (up to 1 year), exactly-once execution, visual console
Express workflows - high-volume (millions), up to 5 minutes, at-least-once, cheaper
Human approval steps (“wait for a manager to click approve”)

flowchart LR
    a[Order event] --> b[Lambda: validate]
    b --> c{Parallel}
    c --> d[Lambda: charge card]
    c --> e[Lambda: reserve stock]
    d & e --> f[Wait: approval?]
    f --> g[Lambda: ship]

Use Step Functions when a question describes a multi-step business process with conditions, retries or human approval. If it’s just “on event, run one function” → Lambda + EventBridge alone.

Not: sinav kisaclari: “olay deseni ile filtreleme / tekrar oynatma” = EventBridge, “cok adimli is akisi / retry / onay adimi” = Step Functions, “dayanikli is kuyrugu” = SQS, “bildirim/duyuru” = SNS.

API Gateway (quick mention)#

Often paired in event-driven questions: managed front door for HTTP APIs with throttling, API keys, usage plans, and direct AWS service integrations. Hands-on: lambda-api-gateway.

Exam check#

Q1: SaaS events from three vendors must be filtered by event type and routed to different Lambda functions, with the ability to replay yesterday’s events after a bug fix. Which service?

A) SNS with subscriptions
B) EventBridge with rules and an archive
C) SQS standard queue
D) CloudWatch Logs

Cevabı göster

Answer: B. Content filtering + SaaS partner sources + replay = EventBridge.

Q2: A loan approval process runs several Lambda functions, waits for a human decision, and must retry failed steps automatically. Which service coordinates it?

A) SQS
B) Amazon EventBridge
C) AWS Step Functions
D) AWS Batch