Advanced C# tutorials, system design deep-dives, and real-world developer tools built in public.
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An open-source .NET tool, built one episode at a time. It simulates fleets of MQTT clients, each with a Last Will, and measures what a broker does under churn: connect latency first, then how long it takes to tell everyone a client has died.
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Build a fleet of 1000 MQTTnet clients with paced connects and a Last Will each, then measure connect latency honestly: why localhost cost 2 seconds per client and why the first numbers measured the harness, not the broker.
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Your AI agent says the sensor is fine, but the sensor died an hour ago. How MQTT retained messages and the Last Will fix that, measured with MQTTnet and Mosquitto: a crash is reported in 0.1 s, a power cut takes 15.6 s.
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MQTT for .NET developers, from the angle of an AI agent reading live device data: broker, topics, wildcards, QoS, retained messages, Last Will, sessions and shared subscriptions, and the traps in each.
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NuGet Audit only checks packages when you restore. Use cve.now's free NuGet feed, its KEV and EPSS triage, and its MCP server to find new CVEs in .NET services you haven't rebuilt.
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Run RabbitMQ locally with Aspire, inject its connection into a .NET 10 API, publish and consume a job, inspect the management UI, and understand what local orchestration does not guarantee.
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How change data capture works in PostgreSQL: the WAL, logical decoding, replication slots and publications. Build a working CDC consumer in .NET with Npgsql and Aspire, and see when CDC beats the Outbox pattern.
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Your solution is full of interfaces and you still can't swap anything. The Dependency Inversion Principle isn't about having abstractions — it's about who owns them. Ports, adapters, and the compile-time test that settles the argument in .NET.
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How the Open/Closed Principle actually plays out when you own a NuGet package, why extension methods are .NET's cheapest OCP tool, and what C# 14 extension members in .NET 10 change for library authors.
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Why architecture tests matter more now that agents write code: enforce Clean Architecture layers and module isolation with NetArchTest, xUnit and .NET 10, and turn the rule into a gate an agent must pass.
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Build .NET integration tests that provision PostgreSQL with Testcontainers, configure WebApplicationFactory, apply EF Core migrations, and run unchanged on a workstation or GitHub Actions.
Read moreWritten by Romain Ottonelli Dabadie, .NET engineer. Messaging, distributed systems and the architecture decisions that still hold up two years later. More about me.
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