Setting the file. One moment.
Subchapter 25.12
references/design-refs/messaging.mdMarkdown17 KBView on GitHub
Pass-2 rubric for every messaging type index.md routes here. Loaded only when the
inventory contains one.
Outcome is confidence: inferred. Never deterministic — Microsoft.EventHub/namespaces
is the one messaging type that is a fast-path row, because owner decision 11.4 made
protocol the whole rubric and left nothing to reason about. Everything below has something
left to reason about.
The recurring shape: Service Bus is one broker with many capabilities; AWS splits those capabilities across SQS, SNS, EventBridge and Amazon MQ. So the namespace does not map to a service — its entities do, and the namespace maps to whatever set they need.
Each is a property of the source entity, readable from IaC. Check them before anything else.
| Candidate | Eliminated when |
|---|---|
| SQS (standard or FIFO) | the entity’s max_message_size_in_kilobytes exceeds 1 MiB (1024 KiB). SQS standard and FIFO accept payloads up to 1 MiB (raised from 256 KiB on 2025-08-04, all commercial Regions + GovCloud; Lambda event source mapping updated to match); Service Bus Premium allows 100 MB. A payload at or under 1 MiB maps to SQS directly — do NOT add a claim-check for it. Only above 1 MiB: route to Amazon MQ, or to SQS with an S3 claim-check — and say which |
| SQS | default_message_ttl exceeds 14 days, the SQS retention ceiling |
| SQS FIFO | duplicate_detection_history_time_window exceeds 5 minutes. FIFO’s dedup window is fixed at 5 minutes; Service Bus allows up to 7 days. A longer window needs an idempotency table, which is application work |
| SQS | messages are scheduled more than 15 minutes ahead (scheduled_enqueue_time). DelaySeconds caps at 900. Route long scheduling to EventBridge Scheduler or Step Functions |
| SQS / SNS | the application speaks AMQP 1.0 or JMS directly rather than through the Service Bus SDK. SQS and SNS are HTTPS APIs; there is no AMQP surface. Amazon MQ is the only candidate that keeps the wire protocol |
| SNS | a subscription filter uses a Service Bus SQL filter that references anything other than equality on user properties — LIKE, IN, arithmetic, sys. system properties. SNS filter policies are attribute matching only |
| SNS | the topic requires ordered delivery with sessions. SNS FIFO topics exist but require a FIFO SQS subscriber and offer no session concept |
| Amazon MQ | the customer’s stated goal includes removing broker management. Amazon MQ is a managed broker, not a serverless queue: it has instance sizes, patch windows and a maintenance model that SQS does not |
| API Gateway WebSocket | the source uses SignalR’s server-to-client streaming or MessagePack hub protocol unchanged. The hub protocol is SignalR-specific; either target is a client rewrite |
Section 1. Whatever survives is the candidate set.
| Source | Target | Why |
|---|---|---|
Microsoft.ServiceBus/namespaces/queues | SQS | A point-to-point queue with competing consumers is exactly SQS |
Microsoft.ServiceBus/namespaces/queues with requires_session = true | SQS FIFO, session id → message group id | Sessions are Service Bus’s ordering primitive and the message group is SQS’s. This is the closest mapping in the file |
Microsoft.ServiceBus/namespaces/topics | SNS | Fan-out to multiple independent subscribers |
Microsoft.ServiceBus/namespaces/topics whose subscriptions carry content-based SQL filters | EventBridge | EventBridge rules match on event content; SNS filter policies match on message attributes. If the filter reads the payload, SNS cannot express it |
Microsoft.ServiceBus/namespaces | the union of what its entities need | The namespace is a container, not a broker instance. See § 3 |
Microsoft.EventHub/namespaces/eventhubs | a topic in MSK, or a stream in Kinesis — whichever the parent namespace resolved to | The hub is not its own service. See § 4 |
Microsoft.SignalRService/SignalR, service_mode = "Serverless" | API Gateway WebSocket API + Lambda | Serverless SignalR already has no hub server; the shape matches |
Microsoft.SignalRService/SignalR, service_mode = "Default" or "Classic" | API Gateway WebSocket API, with the hub server becoming a Fargate service or Lambda | A hub server exists and has to land somewhere |
preferences.json → design_constraints overrides 2.2. A customer who has said “keep
AMQP, we are not rewriting clients” has chosen Amazon MQ, and that answer wins.
Service Bus capabilities and where they land. Anything with no counterpart becomes a
warnings[] entry, never a silent omission.
| Service Bus feature | AWS |
|---|---|
| Dead-letter queue per entity | SQS redrive policy to a DLQ — direct |
lock_duration / peek-lock | SQS visibility timeout — direct |
max_delivery_count | redrive maxReceiveCount — direct |
| Duplicate detection (≤ 5 min) | SQS FIFO content-based dedup — direct |
| Sessions | SQS FIFO message group id — direct |
| Auto-forwarding between entities | no equivalent. Needs a Lambda relay, which is new code |
| Transactions spanning two entities | no equivalent. SQS and SNS have no cross-entity transaction |
| Scheduled messages > 15 min | EventBridge Scheduler — a different service, so a new component |
| Topic subscription rule actions (mutating the message) | no equivalent. SNS and EventBridge filter, they do not transform. Needs a Lambda |
| Geo-disaster recovery pairing | SQS/SNS are regional and already multi-AZ; cross-region needs explicit replication |
Premium namespaces are a signal, not a size. sku = "Premium" buys resource isolation,
VNet integration and 100 MB messages. Do not read it as throughput and do not translate it
into a larger AWS resource — SQS has no instance size. Read it for the message-size
eliminator and for whether VNet integration implies a private-endpoint edge.
Prefer the smaller target set. A topic with three subscriptions and no content filters is SNS plus three SQS queues, not EventBridge plus three rules plus three queues.
Microsoft.ServiceBus/namespaces is the only row here whose target is derived from its
children rather than from itself.
queues and topics child of the namespace first.aws_service is the set of services those children needed —
"SQS", "SQS + SNS", "SQS + SNS + EventBridge", or "Amazon MQ".aws_config so the report can show what the set was
derived from, and emit one warnings[] entry per child consumed this way.compute.md § 3 treats a zero-app plan.An estimate that prices the namespace and each queue has double-counted. An estimate that prices only the namespace has priced nothing.
Microsoft.EventHub/namespaces is a fast-path row: kafka_enabled → MSK, otherwise
Kinesis Data Streams. The hub inside it inherits that decision and must never re-open it.
| Parent resolved to | Hub becomes | Carry across |
|---|---|---|
| MSK | a Kafka topic | partition_count → topic partitions; message_retention (days) → retention.ms; consumer groups → Kafka consumer groups, unchanged in concept |
| Kinesis Data Streams | a stream | partition_count → shard count as the starting point; message_retention → stream retention (24 h default, up to 365 days); consumer groups → enhanced fan-out consumers, which are priced per consumer-shard-hour |
Two traps:
Microsoft.EventHub/namespaces/eventhubs/consumergroups and .../authorizationRules are
Skip Mappings — they are configuration of the hub, not resources of their own.
Per schema-design-aws.md § services[]: aws_service, aws_config (queue type, FIFO
flag, visibility timeout, redrive policy, filter policy shape, partition or shard count),
confidence: "inferred", rubric_applied: "messaging.md", and a rationale naming
which criterion fired and, where an eliminator was involved, which property triggered
it — “SQS FIFO eliminated: duplicate_detection_history_time_window is 1 hour, above the
5-minute FIFO ceiling” is auditable.
Implemented for Service Bus namespaces, queues and topics, Event Hubs entities, and SignalR.
Event Grid does not route here and must not be re-decided in this file:
Microsoft.EventGrid/topics and systemTopics are Direct Mappings, and
eventSubscriptions is a Skip Mapping. That is the right call — an Event Grid topic is
EventBridge regardless of the architecture around it, which is the § 7a.3 admission test.
If you find yourself wanting a rubric for it, the change belongs in
fast-path-services.json, not here: a pattern may never override a deterministic
mapping, so a rubric row here would be unreachable anyway.