Sqs Sns Pub Sub

Hook

Retrying delivery and applying an effect exactly once are separate problems.

Watch

Choose AWS or GCP mapping, change one validated model parameter and load the trace. Provider labels identify concepts; the model never provisions resources or calls a provider account.

How it works

Queue mode shares one consumer group; fan-out creates an independent task per subscriber. Visibility expiry, lost acknowledgments, poison work, bounded retries and an atomic local inbox make pending, duplicate-suppressed and dead-letter outcomes visible.

AWS and GCP comparison

AWS: SQS work queues / SNS fan-out concepts. GCP: Pub/Sub subscription concepts. These services have different ordering, acknowledgment, retention and optional delivery guarantees. The atomic inbox protects a modeled local effect; external email/charges still need their own idempotency protocol. Do not infer universal exactly-once delivery from this diagram.

Try it

Lose the first acknowledgment and compare local deduplication enabled/disabled. Poison one message and account for each group’s completed, dead or pending task. Predict the next modeled decision before advancing.

Complexity

Use the displayed measured operation and explicit bounds. Simulator operations, service quotas, network latency and cloud billing are different measurements. Validate production capacity using the selected product and workload.

Code

The four references implement the core local state model. Provider annotations and UI controls surround that model; the snippets do not authenticate, provision resources or replace a vendor SDK. Worked saga references assume reliable local compensation.

When to use

Use the scenario to explain access patterns, ownership, failure policy and the operational assumptions behind a cloud service choice.

Interview pitfalls

These services have different ordering, acknowledgment, retention and optional delivery guarantees. The atomic inbox protects a modeled local effect; external email/charges still need their own idempotency protocol. Do not infer universal exactly-once delivery from this diagram.

Quiz

Explain one concrete outcome, one provider distinction and one unmodeled production concern.