Client Credentials Flow

Your Orders, Billing, and Reporting services all call Inventory using one shared, static API key.

Now Reporting gets retired. But its copy of the key still works.

Turning that key off would also cut off Orders and Billing, since they're all using the exact same one.

A secret shared by every caller can only ever be revoked for every caller at once. That's exactly what the client credentials flow fixes.

The client credentials flow gives each service its own key: register each one as its own identity in Microsoft Entra ID. Before calling Inventory, a service requests its own short-lived token using its own credentials, and Inventory checks that token on every call, so it can tell exactly who's calling and revoke just one.

Use: Microsoft.Identity.Client (MSAL), Microsoft.Identity.Web

Give every caller its own identity, and you can always cut off one without touching the rest.

A warehouse could hand every delivery driver a copy of the same master keycard.

Instead, each driver gets their own badge, tied to their own name. When one driver leaves the company, security switches off that one badge, and every other driver keeps working exactly as before.

Each service gets its own badge, instead of sharing one master key with everyone else.