Notes from a fractional tech lead: software architecture, code reviews, AI harnesses, design systems and leading small dev teams.https://clementbresson.com/blog/enhttps://clementbresson.com/blog/multi-tenant-data-isolation-four-levels/https://clementbresson.com/blog/multi-tenant-data-isolation-four-levels/A SaaS handling sensitive data has to keep each customer’s data apart. Four levels, from a tenant_id column to dedicated infra, and the one I usually pick.Wed, 16 Sep 2026 00:00:00 GMTArchitecturehttps://clementbresson.com/blog/going-all-in-on-one-day-a-week/https://clementbresson.com/blog/going-all-in-on-one-day-a-week/In a few weeks, five near-identical profiles asked me for the same thing: a developer who watches their back, but not full-time. I am making it my job.Tue, 15 Sep 2026 00:00:00 GMTFractional workhttps://clementbresson.com/blog/the-developer-market-is-shifting/https://clementbresson.com/blog/the-developer-market-is-shifting/Large dev teams are shrinking because of AI. Meanwhile, small businesses are starting to build their own internal tools and will need experts a few days a month.Sun, 13 Sep 2026 00:00:00 GMTThe AI eraFractional workhttps://clementbresson.com/blog/model-orm-vs-domain-model/https://clementbresson.com/blog/model-orm-vs-domain-model/"Model" means both an ORM Model and the DDD domain model. Confusing them makes you think you modelled your business when you only described your tables.Sat, 12 Sep 2026 00:00:00 GMTArchitecturehttps://clementbresson.com/blog/functional-core-imperative-shell/https://clementbresson.com/blog/functional-core-imperative-shell/Gary Bernhardt's 2012 talk Boundaries is still some of the best testing advice around: separate decisions from actions, and pass only values between them.Fri, 11 Sep 2026 00:00:00 GMTArchitectureTestinghttps://clementbresson.com/blog/daily-rates-after-ai/https://clementbresson.com/blog/daily-rates-after-ai/Daily rate grids were built on years of experience because the keyboard capped the gap between good and bad developers. With AI, that bottleneck is gone.Wed, 09 Sep 2026 00:00:00 GMTThe AI eraFractional workhttps://clementbresson.com/blog/dependency-cruiser-as-a-sensor-for-ai-agents/https://clementbresson.com/blog/dependency-cruiser-as-a-sensor-for-ai-agents/dependency-cruiser maps imports and fails CI when a boundary is violated. A sensor for AI agents that only works if the architecture is clear enough to describe.Tue, 08 Sep 2026 00:00:00 GMTAI harnessesArchitecturehttps://clementbresson.com/blog/ai-harness-guides-and-sensors/https://clementbresson.com/blog/ai-harness-guides-and-sensors/A harness is everything in an agent that is not the model. Two axes, four boxes, and a painful conclusion about the harnessability of a codebase.Mon, 07 Sep 2026 00:00:00 GMTAI harnesseshttps://clementbresson.com/blog/distribution-is-the-hard-part/https://clementbresson.com/blog/distribution-is-the-hard-part/Developers often forget that building a product depends on them. Selling, onboarding and keeping customers does not. A simple plan for technical founders.Sun, 06 Sep 2026 00:00:00 GMTFractional workhttps://clementbresson.com/blog/mutation-testing-in-the-age-of-ai-generated-tests/https://clementbresson.com/blog/mutation-testing-in-the-age-of-ai-generated-tests/Coverage measures lines run through, not lines verified. Mutation testing measures whether tests detect bugs, essential once agents write the tests.Sat, 05 Sep 2026 00:00:00 GMTTestingAI harnesseshttps://clementbresson.com/blog/the-part-time-senior-developer/https://clementbresson.com/blog/the-part-time-senior-developer/In companies where the product only supports the business, vibe-coding hits a wall fast. A senior developer a few days a month is often enough to lift it.Fri, 04 Sep 2026 00:00:00 GMTFractional workThe AI erahttps://clementbresson.com/blog/vertical-slice-architecture/https://clementbresson.com/blog/vertical-slice-architecture/When adding one field touches six files in four folders, the feature lives nowhere. Jimmy Bogard's Vertical Slice Architecture flips the way code is organised.Wed, 02 Sep 2026 00:00:00 GMTArchitecturehttps://clementbresson.com/blog/the-next-bottleneck-is-ram/https://clementbresson.com/blog/the-next-bottleneck-is-ram/AI moved the bottleneck from writing to reviewing. The next one is hardware: running five agents in parallel needs a machine not everyone will have.Mon, 31 Aug 2026 00:00:00 GMTThe AI erahttps://clementbresson.com/blog/architecture-rules-that-break-the-build/https://clementbresson.com/blog/architecture-rules-that-break-the-build/With AI, a standardised architecture becomes an asset: every rule a machine can verify is a constraint. The others are only intentions.Sun, 30 Aug 2026 00:00:00 GMTArchitectureAI harnesseshttps://clementbresson.com/blog/test-doubles-dummy-stub-spy-mock-fake/https://clementbresson.com/blog/test-doubles-dummy-stub-spy-mock-fake/The five kinds of test doubles are easy to mix up. One question asked of the double, borrowed from Meszaros, is enough to tell them apart for good.Sat, 29 Aug 2026 00:00:00 GMTTestinghttps://clementbresson.com/blog/choosing-the-right-test-double/https://clementbresson.com/blog/choosing-the-right-test-double/Pure unit test, integration test, a Fake, or a double that records calls: a simple three-question strategy for choosing without hesitation.Fri, 28 Aug 2026 00:00:00 GMTTestinghttps://clementbresson.com/blog/what-does-a-depends-on-b-mean/https://clementbresson.com/blog/what-does-a-depends-on-b-mean/A dependency can be seen by the compiler, by a test, or by nobody. Three questions to stay precise, with developers and with an AI.Thu, 27 Aug 2026 00:00:00 GMTArchitecturehttps://clementbresson.com/blog/what-is-a-layer-in-software-architecture/https://clementbresson.com/blog/what-is-a-layer-in-software-architecture/Abstraction, technical role, call flow, dependencies, deployment: "layer" names five ways of slicing a program, and yours probably has all of them.Wed, 26 Aug 2026 00:00:00 GMTArchitecturehttps://clementbresson.com/blog/what-is-clean-architecture/https://clementbresson.com/blog/what-is-clean-architecture/What Robert C. Martin extracted in 2012 from Hexagonal, Onion and friends: a single rule you can verify in the code, the Dependency Rule.Tue, 25 Aug 2026 00:00:00 GMTArchitecturehttps://clementbresson.com/blog/what-is-onion-architecture/https://clementbresson.com/blog/what-is-onion-architecture/What Jeffrey Palermo proposed in 2008 with Onion Architecture: a single dependency rule so that business code stops paying for every technology change.Mon, 24 Aug 2026 00:00:00 GMTArchitecture