CloudEvents schema, subscriptions, dead-lettering, filtering.

Azure Event Grid — Serverless Event Routing

Azure Event Grid is a fully managed event routing service for reactive, event-driven architectures. Publishers emit events; subscribers receive only the events they care about via filter rules. Built-in Azure sources: Blob Storage (BlobCreated), Resource Groups (resource changes), Container Registry (image push). Custom topics for application events. Event Grid guarantees at-least-once delivery with retry policies. CloudEvents 1.0 schema is the modern standard.

Interactive Pipeline Flow

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📡 Source — system / topic

Event sources: system topics (Azure Storage, Event Hubs, Container Registry — no setup), custom topics (your app publishes events), partner topics (SaaS providers).

Architecture Diagrams

Choosing the right Azure messaging service.

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Key Design Decisions

⚡Event Grid is for events, not commands

Events are notifications: 'BlobCreated', 'OrderPlaced'. Commands are instructions: 'ProcessPayment', 'SendEmail'. Event Grid routes events to interested subscribers. For command processing with FIFO and exactly-once semantics, use Service Bus.

💀Always configure a dead-letter destination

Without a DLQ, events that fail all retries are silently dropped. Configure a Storage Blob container as DLQ for all production subscriptions. Monitor DLQ blob count and alert when nonzero.

🔔Use event filters to reduce unnecessary invocations

Without filters, every blob change event triggers your function — including temporary files. Filter by event type (BlobCreated not BlobDeleted) and subject prefix (/uploads/ not /temp/). Reduces cost and false triggers.

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