MB-820· AssociateCurrent exam

Business Central Developer

By Emil Björk · Microsoft business apps consultant, Gothenburg

AL development: extensions, events, testing, and AppSource-ready code.

15 guides · about 42 minutes of reading · Official exam page and skills outline on Microsoft Learn →

This is a reading order, not exam-dump material. The areas below are how this site groups what MB-820covers; Microsoft's study guide on the exam page lists the measured skills and their weightings, and that outline changes between releases. Read the guides for the concepts, then spend the rest of your preparation in a trial environment.

1.AL and the extension model

  1. Writing your first AL extension3 minA first-walkthrough of building, publishing, and running a basic AL extension for Business Central — toolchain, project structure, and deployment.
  2. AL extension architecture2 minHow AL extensions are structured in Business Central — objects, namespaces, app.json, dependencies, and the runtime model.
  3. AL events and integration patterns2 minHow AL events let extensions hook into Business Central — business events, integration events, subscriber patterns, and what to avoid.
  4. Per-tenant extensions vs AppSource2 minWhen to ship a Business Central extension as a per-tenant (PTE) vs publishing to AppSource — distribution, validation, and lifecycle differences.

2.Testing, debugging, and errors

  1. The AL test framework2 minWriting automated tests in AL — test codeunits, test runners, test isolation, and the libraries Microsoft ships with Business Central.
  2. The AL debugger in Business Central — a deep dive3 minHow the AL debugger works for developing Business Central extensions — VS Code integration, snapshot debugging, attaching to sessions.
  3. AL compiler errors in Business Central6 minThe AL compiler errors every Business Central developer hits — AL0118, AL0132, AL0185, AL0296, AL0432, AL0603, AL0604, ID-range and symbol errors — with cause, fix, and prevention.
  4. AL runtime errors in Business Central7 minThe Business Central runtime errors AL developers and admins meet most — record already exists, does not exist, modified by another user, string length, locks and deadlocks, G/L inconsistency — with fixes.

3.APIs and integration

  1. The Business Central API and OData services3 minHow external systems talk to Business Central — the v2.0 REST API, OData web services, bound actions, and call limits.
  2. Business Central web services2 minThe classic OData and SOAP web services in Business Central — how they differ from the v2.0 API, and when to use them.
  3. Webhooks in Business Central2 minHow webhook subscriptions work in Business Central — subscribing, renewing, payloads, and the realities of consuming change notifications.

4.Lifecycle, performance, and telemetry

  1. Business Central CI/CD with AL-Go2 minHow AL-Go for GitHub turns an AL extension repo into a build-test-deploy pipeline — secrets, environments, and continuous delivery.
  2. Upgrading AL code across Business Central versions2 minHow to keep AL extensions working through Business Central's twice-yearly release waves — breaking changes, deprecations, and code migration patterns.
  3. Business Central performance tuning2 minWhere Business Central performance problems come from, and the AL and configuration patterns that fix them — keys, queries, locking, and async jobs.
  4. Business Central telemetry and monitoring2 minHow to wire Business Central into Application Insights, what to watch for, and how to use telemetry to diagnose and prevent incidents.

Frequently asked questions

Is MB-820 still available?

Yes. MB-820 (Business Central Developer) is a current exam as of the last review of this page. Check the official Microsoft Learn exam page for the live skills outline, languages, and any scheduled retirement.

How long does the reading on this page take?

The 15 guides total roughly 1 hour of reading (42 minutes). They cover the concepts the exam assumes, not exam questions — pair them with the official learning path and hands-on time in a trial environment.

Where is the official skills outline for MB-820?

On Microsoft Learn, at the exam page linked from this page. The areas here are this site's grouping of the topics; the official study guide lists the measured skills and their weightings and is the only authoritative source.

Other ERP — Business Central exams

Exam status reflects Microsoft's public retirement announcements as of August 2026. This site is independent of Microsoft; exam names and codes are Microsoft's.