https://archiboard.cortesi.be/ Drawings and notes on building web applications in .NET en https://archiboard.cortesi.be/craft/fourteen-years-of-dotnet-web-applications/ https://archiboard.cortesi.be/craft/fourteen-years-of-dotnet-web-applications/ Thu, 20 Aug 2026 09:00:00 GMT Craft & Judgment From ASP.NET MVC 2 and Entity Framework 4 to .NET 10. Hosting, configuration, resilience and telemetry became somebody else's problem. Tenancy, migrations, cost, saying no and naming things are still mine. https://archiboard.cortesi.be/resilience/load-testing-a-tenant-shaped-system/ https://archiboard.cortesi.be/resilience/load-testing-a-tenant-shaped-system/ Wed, 12 Aug 2026 09:00:00 GMT Resilience & Scale Five hundred identical virtual users prove nothing. Your tenants are three big ones and forty small ones, and only that shape finds the noisy neighbour. https://archiboard.cortesi.be/cloud/the-cost-sheet-what-a-tenant-actually-costs-you/ https://archiboard.cortesi.be/cloud/the-cost-sheet-what-a-tenant-actually-costs-you/ Thu, 16 Jul 2026 09:00:00 GMT Cloud & Operations Cost per tenant is an allocation, not a measurement. The rules of the allocation are a product decision, and finance will treat the first number you give them as the truth. https://archiboard.cortesi.be/boundaries/idempotent-consumers-and-the-duplicate-you-will-receive/ https://archiboard.cortesi.be/boundaries/idempotent-consumers-and-the-duplicate-you-will-receive/ Thu, 11 Jun 2026 09:00:00 GMT Services & Boundaries At-least-once means twice, eventually. Make the operation naturally repeatable, or let a unique constraint on an inbox table settle the argument. https://archiboard.cortesi.be/craft/how-i-draw-a-system-before-i-build-it/ https://archiboard.cortesi.be/craft/how-i-draw-a-system-before-i-build-it/ Tue, 02 Jun 2026 09:00:00 GMT Craft & Judgment Pen first, then SVG, then code. One drawing per question, a verb on every arrow, and a new sheet rather than an edited one when the system changes. https://archiboard.cortesi.be/identity/entra-id-multi-tenant-applications-and-the-admin-consent-dance/ https://archiboard.cortesi.be/identity/entra-id-multi-tenant-applications-and-the-admin-consent-dance/ Thu, 28 May 2026 09:00:00 GMT Identity & Access One app registration, any customer directory. The consent flow is well documented. What to trust when the music stops is not. https://archiboard.cortesi.be/cloud/opentelemetry-traces-that-carry-the-tenant-id/ https://archiboard.cortesi.be/cloud/opentelemetry-traces-that-carry-the-tenant-id/ Thu, 14 May 2026 09:00:00 GMT Cloud & Operations A trace without the tenant id is a trace you cannot filter during an incident. Put it in baggage once at the edge, copy it to every span, and make it survive the queue. https://archiboard.cortesi.be/resilience/background-work-and-the-job-you-must-not-run-twice/ https://archiboard.cortesi.be/resilience/background-work-and-the-job-you-must-not-run-twice/ Thu, 23 Apr 2026 09:00:00 GMT Resilience & Scale A BackgroundService with a timer is correct on one instance and wrong on two. The second instance is not a bug you can test for locally. https://archiboard.cortesi.be/tenancy/onboarding-a-tenant-is-a-saga/ https://archiboard.cortesi.be/tenancy/onboarding-a-tenant-is-a-saga/ Tue, 07 Apr 2026 09:00:00 GMT Tenancy & Data Six steps across five systems that share no transaction. Treat it as a saga with compensations, make every step idempotent, and send the mail last. https://archiboard.cortesi.be/boundaries/the-transactional-outbox-with-ef-core-and-service-bus/ https://archiboard.cortesi.be/boundaries/the-transactional-outbox-with-ef-core-and-service-bus/ Thu, 05 Mar 2026 09:00:00 GMT Services & Boundaries You cannot commit a row and publish a message in one transaction. Write the message to a table instead and let a relay carry it to the bus. https://archiboard.cortesi.be/identity/authorization-policies-requirements-and-handlers-roles-that-belong-to-a-tenant/ https://archiboard.cortesi.be/identity/authorization-policies-requirements-and-handlers-roles-that-belong-to-a-tenant/ Tue, 24 Feb 2026 09:00:00 GMT Identity & Access A role claim without a tenant next to it is a global role, and a global role in a multi-tenant product is a bug waiting for the second tenant. https://archiboard.cortesi.be/craft/saying-no-to-the-feature-that-breaks-the-tenancy-model/ https://archiboard.cortesi.be/craft/saying-no-to-the-feature-that-breaks-the-tenancy-model/ Thu, 19 Feb 2026 09:00:00 GMT Craft & Judgment A report across sister companies, a user shared between tenants. Each sounds small, and each turns the tenant boundary into a suggestion. Say no with a drawing, and bring the alternative on the same sheet. https://archiboard.cortesi.be/cloud/app-service-container-apps-or-aks/ https://archiboard.cortesi.be/cloud/app-service-container-apps-or-aks/ Tue, 10 Feb 2026 09:00:00 GMT Cloud & Operations In 2014 the choice was a Cloud Services role, the new Azure Websites, or a virtual machine you patched yourself. Container Apps eventually put a rung in the middle of the ladder, and that is where most small teams should stand. https://archiboard.cortesi.be/resilience/caching-layers-for-a-web-application/ https://archiboard.cortesi.be/resilience/caching-layers-for-a-web-application/ Tue, 27 Jan 2026 09:00:00 GMT Resilience & Scale Two layers, one key format. If the tenant id is not in the key, the cache is a data leak with good response times. https://archiboard.cortesi.be/tenancy/ef-core-query-filters-as-a-tenant-fence/ https://archiboard.cortesi.be/tenancy/ef-core-query-filters-as-a-tenant-fence/ Mon, 19 Jan 2026 09:00:00 GMT Tenancy & Data HasQueryFilter is the best default a shared-row database can have. It is not a security boundary, and there are three doors around it. https://archiboard.cortesi.be/boundaries/cqrs-without-the-ceremony/ https://archiboard.cortesi.be/boundaries/cqrs-without-the-ceremony/ Thu, 18 Dec 2025 09:00:00 GMT Services & Boundaries Two models, one database, no mediator. Separate the shapes you write from the shapes you read and stop there until something forces you further. https://archiboard.cortesi.be/resilience/rate-limiting-the-noisy-neighbour/ https://archiboard.cortesi.be/resilience/rate-limiting-the-noisy-neighbour/ Thu, 04 Dec 2025 09:00:00 GMT Resilience & Scale The limit is not there to protect the API. It is there to protect the database that every other tenant is also using. https://archiboard.cortesi.be/cloud/feature-flags-ship-dark-reveal-per-tenant/ https://archiboard.cortesi.be/cloud/feature-flags-ship-dark-reveal-per-tenant/ Thu, 20 Nov 2025 09:00:00 GMT Cloud & Operations A flag is a switch you intend to remove. An entitlement is a promise you intend to keep. Mixing them is how a pricing rule ends up in a config store. https://archiboard.cortesi.be/identity/openid-connect-one-issuer-many-tenants/ https://archiboard.cortesi.be/identity/openid-connect-one-issuer-many-tenants/ Thu, 13 Nov 2025 09:00:00 GMT Identity & Access Every tenant wants to bring its own identity provider. The OIDC handler was designed for one. Here is how to make them agree without lying to the framework. https://archiboard.cortesi.be/boundaries/versioning-a-public-api-for-a-thousand-tenants/ https://archiboard.cortesi.be/boundaries/versioning-a-public-api-for-a-thousand-tenants/ Thu, 30 Oct 2025 09:00:00 GMT Services & Boundaries The version is a promise to people you will never meet. Put it in the URL, keep changes additive, and treat a sunset date as a project rather than a header. https://archiboard.cortesi.be/craft/reading-microsoft-docs-like-an-architect/ https://archiboard.cortesi.be/craft/reading-microsoft-docs-like-an-architect/ Tue, 14 Oct 2025 09:00:00 GMT Craft & Judgment The Architecture Center, the product docs and the Well-Architected Framework answer three different questions. Read the limits page first, check the date, and go to the samples repo when the words stop making sense. https://archiboard.cortesi.be/tenancy/three-ways-to-slice-a-tenant/ https://archiboard.cortesi.be/tenancy/three-ways-to-slice-a-tenant/ Thu, 02 Oct 2025 09:00:00 GMT Tenancy & Data Database, schema or row. The choice you make in month one is the one you live with in year six. https://archiboard.cortesi.be/tenancy/per-tenant-configuration-and-entitlements/ https://archiboard.cortesi.be/tenancy/per-tenant-configuration-and-entitlements/ Tue, 23 Sep 2025 09:00:00 GMT Tenancy & Data A feature flag says whether the code path is switched on. An entitlement says whether this tenant paid for it. Confuse the two and support will confuse them for you. https://archiboard.cortesi.be/cloud/deployment-stamps-cloning-the-whole-cell/ https://archiboard.cortesi.be/cloud/deployment-stamps-cloning-the-whole-cell/ Thu, 04 Sep 2025 09:00:00 GMT Cloud & Operations A stamp is a unit of scale and a unit of blast radius. The second property is the one that pays for the first. https://archiboard.cortesi.be/cloud/bicep-and-the-environments-ladder/ https://archiboard.cortesi.be/cloud/bicep-and-the-environments-ladder/ Thu, 28 Aug 2025 09:00:00 GMT Cloud & Operations One module, four parameter files, and a what-if that a human actually reads. Everything else is how environments drift apart. https://archiboard.cortesi.be/identity/api-keys-client-credentials-and-machine-access/ https://archiboard.cortesi.be/identity/api-keys-client-credentials-and-machine-access/ Tue, 19 Aug 2025 09:00:00 GMT Identity & Access Customers integrate with a cron script long before they integrate with your SDK. Give the script a key, give the platform a token, and never store either in the clear. https://archiboard.cortesi.be/boundaries/bounded-contexts-before-microservices/ https://archiboard.cortesi.be/boundaries/bounded-contexts-before-microservices/ Wed, 09 Jul 2025 09:00:00 GMT Services & Boundaries Find the seams with language, rate of change and team shape. Draw the context map first, and only then decide what deploys separately. https://archiboard.cortesi.be/resilience/retries-timeouts-and-the-circuit-breaker/ https://archiboard.cortesi.be/resilience/retries-timeouts-and-the-circuit-breaker/ Thu, 26 Jun 2025 09:00:00 GMT Resilience & Scale Three retries and a two second wait is not a resilience strategy. It is a load generator with good intentions. https://archiboard.cortesi.be/tenancy/sharding-azure-sql-with-elastic-pools-and-a-catalog/ https://archiboard.cortesi.be/tenancy/sharding-azure-sql-with-elastic-pools-and-a-catalog/ Tue, 17 Jun 2025 09:00:00 GMT Tenancy & Data A shard is a database, a pool is a budget, and the catalog is the only thing that knows which is which. Keep it small enough to understand at three in the morning. https://archiboard.cortesi.be/identity/aspnet-core-identity-or-azure-ad-b2c-choosing-the-front-door/ https://archiboard.cortesi.be/identity/aspnet-core-identity-or-azure-ad-b2c-choosing-the-front-door/ Tue, 06 May 2025 09:00:00 GMT Identity & Access Own the password table or rent the login page. Both are fine choices; what is not fine is owning it by accident.