Event Grid, Event Hub, and Service Bus in Azure
Event Grid, Event Hub, and Service Bus in Azure
A Complete Guide for Azure Data Engineers
In modern data platforms, real-time data processing and event-driven architectures play a crucial role. Azure provides three powerful messaging and eventing services that often confuse beginners and even intermediate engineers:
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Azure Event Grid
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Azure Event Hub
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Azure Service Bus
Although all three deal with “events” and “messages,” they serve very different purposes. Understanding when and how to use each one is an essential skill for an Azure Data Engineer.
Let’s break them down in a simple and practical way.
1. Azure Event Grid – The Event Router
What is Event Grid?
Azure Event Grid is an event routing service. It reacts to changes in Azure resources or custom applications and routes those events to subscribers.
Think of it as:
“Something happened → notify interested systems immediately.”
It is reactive, lightweight, and designed for event-driven architectures.
Key Use Cases
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Trigger Azure Functions when a blob is uploaded
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Start a Data Factory pipeline when a file arrives
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Notify systems when a VM is created or deleted
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Build serverless workflows
Characteristics
| Feature | Description |
|---|---|
| Purpose | Event notification and routing |
| Message size | Small (up to 1 MB) |
| Retention | No long-term storage |
| Delivery | Push-based |
| Ordering | Not guaranteed |
| Throughput | High |
| Latency | Very low |
Example
A file is uploaded into Azure Blob Storage:
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Blob Storage raises an event
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Event Grid receives it
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Event Grid triggers:
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Azure Function
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Logic App
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Data Factory pipeline
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Perfect for automation and orchestration.
2. Azure Event Hub – The Big Data Streaming Platform
What is Event Hub?
Azure Event Hub is a high-throughput data streaming service designed for ingesting massive volumes of events or telemetry.
Think of it as:
“Millions of events per second flowing continuously.”
It is similar to Apache Kafka in concept.
Key Use Cases
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IoT telemetry ingestion
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Application logs and metrics
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Real-time analytics pipelines
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Streaming data to:
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Azure Stream Analytics
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Azure Synapse
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Azure Databricks
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Characteristics
| Feature | Description |
|---|---|
| Purpose | Event streaming & ingestion |
| Message size | Up to 1 MB |
| Retention | 1–7 days (default), configurable |
| Delivery | Pull-based |
| Ordering | Preserved within partitions |
| Throughput | Extremely high |
| Consumers | Multiple consumer groups |
Example
IoT devices sending sensor data:
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Devices send telemetry → Event Hub
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Stream Analytics processes data
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Data is stored in:
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Azure Data Lake
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Synapse
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Power BI for real-time dashboards
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This is the backbone of real-time analytics.
3. Azure Service Bus – The Enterprise Messaging System
What is Service Bus?
Azure Service Bus is a message broker for reliable communication between applications.
Think of it as:
“Guaranteed message delivery between systems.”
It is ideal for transactional systems and enterprise integration.
Core Components
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Queues → One-to-one communication
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Topics & Subscriptions → One-to-many communication
Key Use Cases
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Decoupling microservices
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Financial transactions
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Order processing systems
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Workflow coordination
Characteristics
| Feature | Description |
|---|---|
| Purpose | Reliable messaging |
| Message size | Up to 256 KB (Standard), 1 MB (Premium) |
| Retention | Until consumed |
| Delivery | Pull-based |
| Ordering | Supported |
| Transactions | Supported |
| Dead-letter queue | Supported |
Example
E-commerce order processing:
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Order placed → Message sent to Service Bus Queue
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Payment service consumes message
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Inventory service processes it
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Shipping service continues workflow
This ensures no message is lost.
4. Comparison Table
| Feature | Event Grid | Event Hub | Service Bus |
|---|---|---|---|
| Primary role | Event routing | Event streaming | Message brokering |
| Typical workload | Reactive automation | Big data ingestion | Business workflows |
| Data volume | Low–medium | Very high | Medium |
| Message durability | Short-lived | Configurable retention | Stored until consumed |
| Ordering | No | Yes (per partition) | Yes |
| Transactions | No | No | Yes |
| Real-time analytics | ❌ | ✅ | ❌ |
| Workflow integration | ⚠️ | ❌ | ✅ |
5. How Azure Data Engineers Use Them Together
In real-world architectures, these services often work together:
Example architecture:
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Event Grid
Detects a file upload in Blob Storage. -
Service Bus
Sends a message to trigger a processing workflow. -
Event Hub
Streams processed data for analytics dashboards.
Flow:
This creates:
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Event-driven automation
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Reliable workflows
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High-scale analytics pipelines
6. When to Use What?
Ask these questions:
| Question | Use |
|---|---|
| Do I need to react to an event immediately? | Event Grid |
| Am I streaming huge volumes of data? | Event Hub |
| Do I need guaranteed delivery and transactions? | Service Bus |
| Is this analytics data? | Event Hub |
| Is this business workflow data? | Service Bus |
8. Conclusion
Understanding the differences between Event Grid, Event Hub, and Service Bus is foundational for designing scalable, reliable, and real-time Azure data platforms.
Each service has a unique role:
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Event Grid → Reactive
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Event Hub → Streaming
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Service Bus → Transactional Messaging
As an Azure Data Engineer, choosing the right service ensures:
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Better performance
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Lower cost
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Cleaner architecture
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Highly scalable pipelines
Mastering these three services puts you one step closer to building enterprise-grade data solutions in Azure.
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