Microsoft MB-820 Cheat Sheet: BC Developer

May 1, 2026

Review the Microsoft Dynamics 365 Business Central Developer (MB-820) scope, AL extensions, objects, events, APIs, integrations, performance, testing, deployment, and upgradeability traps before practicing.

On this page

MB-820 is the developer route for Business Central. Keep the exam lens on AL extensions, object design, events, APIs, integrations, testing, deployment, performance, and upgrade-safe customization.

Use this with practice. Review the Business Central developer checkpoints, then return to the MB-820 page for sample questions and update tracking.

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Exam snapshot

Field	Detail
Issuer	Microsoft
Certification lane	Dynamics 365 Business Central Developer
Exam code	MB-820
Main scope	AL development, extensions, objects, events, APIs, integrations, testing, deployment, performance, and upgradeability
IT Mastery status	Sample questions available

Business Central developer map

Area	What to know	Common trap
AL extensions	App structure, dependencies, permissions, deployment, and upgrade behavior	Modifying base behavior in an unsupported way
Objects and events	Tables, pages, reports, codeunits, events, subscribers, and validation	Adding logic in the wrong layer
APIs and integration	Web services, APIs, authentication, error handling, and external systems	Treating integration as only data copy
Testing and quality	Test codeunits, data setup, debugging, telemetry, and regression	Deploying without testing important scenarios
Performance and lifecycle	Query design, background work, source control, app versions, and environments	Ignoring performance until production users complain

Must-know distinctions

Distinction	How to decide
Extension vs base modification	Extensions add supported behavior; base modification creates upgrade risk.
Event publisher vs subscriber	Publishers expose extensibility points; subscribers respond to them.
Table extension vs page extension	Table extensions add data; page extensions change user experience.
API page vs regular page	API pages support integrations; regular pages serve user interaction.
Functional setup vs developer extension	Setup configures standard behavior; extensions add custom behavior.

High-yield checklist

Use AL extensions and event subscribers for upgrade-safe customization.
Choose the right object type for the business need.
Keep validation close to the data or process it protects.
Secure APIs and integrations with identity and permission controls.
Write tests for important custom behavior.
Monitor performance and avoid inefficient data access.
Version and deploy extensions through a controlled lifecycle.

Common traps

Putting business logic only in the user interface.
Building integrations without failure handling.
Treating extension deployment as a manual copy task.
Forgetting permissions for custom objects or APIs.
Ignoring upgradeability when solving a short-term request.

Practice strategy

For MB-820 misses, decide whether the problem is AL structure, object choice, events, integration, testing, deployment, performance, or security. Strong answers keep customization maintainable and upgrade-aware.

Revised on Monday, May 25, 2026