// essays
Architecture, code design and AI inside business systems, written from production work. Short, opinionated, with code you can run.
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Part 2 of the locking series: the optimistic concurrency EF Core gives you for a rowversion column, measured under 50 concurrent transfers. How the token becomes a WHERE predicate, how to handle DbUpdateConcurrencyException without a stale change tracker, which retry policy does not stampede, and where a hot row breaks it.
Silo, pooled compute with siloed data, or one partitioned database: the layout sets the isolation boundaries. The leak is always the same mistake, a request that reached the data layer without knowing its tenant. Put the tenant id in the token, resolve it once at the edge, let the data layer apply it to reads and writes, and hand it explicitly to workers and jobs.
There is no best architecture. Every decision gives you something and takes something away. The price starts on day one, the benefit only when the need shows up. Why moving code to another server does not fix coupling.
A customer support agent built with the Microsoft Agent Framework inside a clean architecture solution: the abstraction in Application, Ollama and the C# tools in Infrastructure, a domain that never hears about AI, and a model that can only ask for the methods you chose to expose.
A model turns text into text and nothing else. The harness is the loop, the tools, the context and the guardrails around it, and it is the part that decides whether an AI tool works. Agent harness, eval harness, and why you should compare harnesses instead of models.
Greenfield project, small team, no microservices on day one. Bounded contexts as separate projects, one schema per module, messages between modules, and why the split to services later is a deployment decision and not a rewrite.
The 1-to-1 mapping trap, the two jobs a DTO actually does (composition and boundary isolation), data on the inside versus outside, and how MediatR queries and commands replace CRUD wrappers around tables.
Five rules for DTOs in modern .NET: no behavior, no encapsulation, properties instead of fields, the Dto suffix as a last resort, one type per boundary, plus the DataAnnotations trap on positional records.
A LIMS case study: two lab technicians dispatch material from the same aliquot, and an in-process lock (lock, SemaphoreSlim) stops working the moment a second instance is deployed.
A five-part series on race conditions in .NET and how to fix them at the right layer: in-process locks, database locks, optimistic concurrency and distributed locks.
Step by step guide to adding ASP.NET Core Identity to a Blazor app inside a .NET Aspire solution, including the database, migrations and login flow.