F&O Architecture: The Big Picture
Understand the cloud and on-premises architecture of Dynamics 365 Finance and Operations apps and how they connect to the Microsoft ecosystem.
F&O Architecture: The Big Picture
Welcome to the MB-500 study guide. Before you write a single line of X++, you need to understand what Dynamics 365 Finance and Operations actually is, where it runs, and how it connects to the rest of the Microsoft platform.
Think of F&O as a massive business brain that lives in the cloud.
Finance and Operations (F&O) is an ERP system — it manages money, inventory, manufacturing, and supply chains for large organisations. It is like the central nervous system of a business. The “cloud” version runs in Microsoft’s Azure data centres, and Microsoft handles the servers, updates, and infrastructure. There is also an “on-premises” version where the company runs it on their own servers, but cloud is the standard path today.
F&O does not work alone — it connects to Power Platform (for low-code apps), Dataverse (shared data), Azure services (AI, IoT, analytics), and Microsoft 365 (Teams, Outlook). As a developer, you extend all of this.
Cloud vs On-Premises
| Aspect | Cloud (Standard) | On-Premises |
|---|---|---|
| Hosted by | Microsoft Azure | Your own servers (Azure Service Fabric) |
| Updates | Microsoft pushes platform updates automatically | You control update timing |
| Infrastructure | Fully managed — no hardware to maintain | You manage servers, storage, networking |
| LCS integration | Full integration — environment management, deployments, monitoring | Limited — some LCS features not available |
| Cost model | Subscription (per user/month) | Licence + infrastructure costs |
| Customisation | Extension model only (no overlayering) | Extension model only (same as cloud) |
| Scalability | Azure auto-scaling | Manual capacity planning |
| Best for | Most organisations — recommended default | Regulated industries requiring data sovereignty |
👨💻 Elena’s perspective: “PacificForge started on-premises because our factory floor systems required local connectivity. Two years later, we migrated to cloud. The lesson? Start cloud unless you have a regulatory or connectivity reason not to. The development experience is identical — your X++ code works the same in both.”
The Application Stack
F&O is built in layers. Understanding these layers helps you know where your code fits.
| Layer | What It Contains | Who Manages It |
|---|---|---|
| Platform | AOS runtime, batch framework, security, OData, web client | Microsoft — updated automatically |
| Application Foundation | Base tables, number sequences, workflow engine, reporting framework | Microsoft — you extend, never modify |
| Application Suite | Finance, Supply Chain, Manufacturing, HR modules | Microsoft — you extend via CoC and events |
| Your Extensions | Custom models, CoC extensions, event handlers, data entities | You — deployed as packages |
| ISV Solutions | Third-party add-ons from partners | ISV — deployed as separate packages |
🎓 Sophie’s first day at Ferris Industries: “Diana showed me the Application Explorer in Visual Studio. I was overwhelmed — thousands of tables, classes, and forms. Carl said: ‘Think of it as layers. Microsoft builds the foundation. We build on top. Our code lives in our own model and never touches theirs.’ That made everything click.”
The Microsoft Ecosystem
F&O does not live in isolation. As a developer, you will integrate with:
| Service | How F&O Connects | Developer Relevance |
|---|---|---|
| Power Platform | Dual-write, virtual entities, connectors | Build Power Apps on F&O data |
| Dataverse | Shared data layer with customer engagement apps | Sync data via dual-write |
| Azure Services | Key Vault, Service Bus, Event Grid, Logic Apps | Secure secrets, event-driven integration |
| Microsoft 365 | Excel edit-in-place, Teams notifications | OData for Excel, business events for Teams |
| Azure DevOps | Source control, build pipelines, CI/CD | Manage code and deployments |
Exam tip: Extension model is the only way
The exam may ask about modifying base Microsoft code. The answer is always: you cannot. Overlayering (modifying base code in a higher model layer) is fully blocked. The only supported approach is the extension model — Chain of Command, event handlers, and table/form extensions. This applies equally to cloud and on-premises deployments.
Fleet Management — The Learning Sandbox
Microsoft provides the Fleet Management sample application as a learning tool. It is a simplified vehicle rental system that demonstrates F&O development patterns: tables, forms, classes, reports, workflows, and data entities.
When the exam references “sample applications,” they usually mean Fleet Management. It is pre-installed in every development environment.
Elena is advising a new client on their F&O deployment. The client has no data sovereignty requirements and wants minimal infrastructure management. Which deployment should she recommend?
Sophie wants to fix a bug in a standard Microsoft form. What approach should she use?
Which Microsoft service provides bidirectional real-time data synchronisation between F&O and customer engagement apps?
Next up: Lifecycle Services: Environments & Deployments — the hub for managing F&O environments, deployments, and troubleshooting.