Messaging

Signals (Decision Criteria)

Pub/Sub

• Multiple subscribers, broadcast → SNS (pub/sub pattern)
• Single consumer, durability → SQS (queue pattern)
• Exactly-once delivery → SNS FIFO + SQS FIFO (deduplication enabled)
• Real-time, low latency → SNS (vs SQS polling delay)

Cloud Tasks

• HTTP callback execution → EventBridge + SNS/SQS (route to Lambda/Fargate)
• Delayed/scheduled queue → SQS + Lambda (ScheduledEvents)

6-Criteria Rubric

Apply in order:

1. Eliminators: Does GCP config require AWS-unsupported features? If yes: switch
2. Operational Model: Managed (SNS, SQS, EventBridge) vs Custom queue?
   • Prefer managed
3. User Preference: From preferences.json: design_constraints.availability?
   • SNS and SQS are multi-AZ by default — no special config needed for HA
   • If ordering or exactly-once delivery required → SQS FIFO (see Eliminators)
4. Feature Parity: Does GCP config need features unavailable in AWS?
   • Example: Pub/Sub ordering guarantee → SQS FIFO (has ordering)
5. Cluster Context: Are other resources using SNS/SQS? Match if possible
6. Simplicity: SNS + SQS (coupled) vs separate services

Examples

Example 1: Pub/Sub Topic (broadcast)

• GCP: google_pubsub_topic (name=”user-events”, message_retention_duration=”7d”)
• Signals: Broadcast events, multiple subscribers likely
• Criterion 1 (Eliminators): PASS (retention not critical for broadcast)
• Criterion 2 (Operational Model): SNS (pub/sub)
• → AWS: SNS Topic (Standard)
• Note: SNS does not support message retention like GCP Pub/Sub. If retention is critical, use SQS instead.
• Confidence: inferred

Example 2: Pub/Sub Topic (exactly-once)

• GCP: google_pubsub_topic + google_pubsub_subscription (exactly_once_delivery=true)
• Signals: Exactly-once delivery required
• Criterion 1 (Eliminators): Exactly-once required → use SNS FIFO + SQS FIFO
• → AWS: SNS FIFO Topic + SQS FIFO Queue (deduplication enabled)
• Confidence: inferred

Example 3: Cloud Tasks Queue (scheduled)

• GCP: google_cloud_tasks_queue (rate_limits=1000 msg/sec, retry_config=[max_retries=5])
• Signals: Task scheduling, retry configuration
• Criterion 1 (Eliminators): PASS
• → AWS: SQS (standard) + Lambda ScheduledEvents (for scheduling)
• Confidence: inferred

Output Schema