https://www.christoph-sens.com/blog/ Success stories and articles by Christoph Sens on Kotlin, Java, AWS, architecture and software development. en https://www.christoph-sens.com/blog/circuit-breakers-for-legacy-backends/ https://www.christoph-sens.com/blog/circuit-breakers-for-legacy-backends/ Sat, 07 Nov 2026 00:00:00 GMT Why batching and rate limiting alone are not enough, how a circuit breaker coupled with queue processing keeps the dead letter queue empty – and how latency-based configuration brought an overloaded legacy system back to 99.9% availability. https://www.christoph-sens.com/blog/hexagonal-architecture-in-practice/ https://www.christoph-sens.com/blog/hexagonal-architecture-in-practice/ Sat, 07 Nov 2026 00:00:00 GMT While replacing a monolith in the energy sector step by step, I build every new application hexagonally: model, application, adapter and bootstrap as separate Gradle modules, enforced with ArchUnit. What this gives decision-makers, architects and developers, why it speeds up AI-assisted development – and where it hurts. https://www.christoph-sens.com/blog/keeping-dependencies-up-to-date/ https://www.christoph-sens.com/blog/keeping-dependencies-up-to-date/ Sat, 07 Nov 2026 00:00:00 GMT Software ages even when nobody touches it. Why many small updates cost less than rare big migrations, how Renovate and Dependabot take load off developers – and when the process can be fully automated, given good enough test coverage. https://www.christoph-sens.com/blog/most-integration-tests-are-unit-tests-in-disguise/ https://www.christoph-sens.com/blog/most-integration-tests-are-unit-tests-in-disguise/ Sat, 07 Nov 2026 00:00:00 GMT A @SpringBootTest is quick to write and expensive to run. Testing domain logic through integration tests costs context restarts, Testcontainers start-ups and long pipelines. How hexagonal architecture puts the test pyramid back on its feet – and which Spring levers take a pipeline from 40 to 20 minutes. https://www.christoph-sens.com/success-stories/monolith-replacement/ https://www.christoph-sens.com/success-stories/monolith-replacement/ Sat, 07 Nov 2026 00:00:00 GMT An energy supplier is replacing an unmaintainable PHP monolith for market communication step by step. In a load test, the new aggregation processed 70,000 market data records in under a minute. https://www.christoph-sens.com/success-stories/tariff-change-e-mobility/ https://www.christoph-sens.com/success-stories/tariff-change-e-mobility/ Sat, 07 Nov 2026 00:00:00 GMT At the turn of the year, a car maker’s charging tariffs change. Hardly anyone wanted to take on the change in the billing backend – I took it on as a new team member. https://www.christoph-sens.com/blog/what-the-test-suite-does-not-find/ https://www.christoph-sens.com/blog/what-the-test-suite-does-not-find/ Mon, 02 Nov 2026 00:00:00 GMT Passing all 715 cases of the official test suite is not enough. Fuzzing, differential tests, mutation testing and a close reading of the specification found bugs in Treetrail and Eclipse Parsson that no test suite shows – and a bug in the test suite itself. https://www.christoph-sens.com/blog/why-i-wrote-treetrail-jsonpath-for-java/ https://www.christoph-sens.com/blog/why-i-wrote-treetrail-jsonpath-for-java/ Fri, 09 Oct 2026 00:00:00 GMT Treetrail brings RFC 9535, the JSONPath standard, to Java: the same results as in other languages, safe with untrusted queries, adapters for Jackson, Gson and JSON-P – and an orderly way off Jayway JsonPath. https://www.christoph-sens.com/success-stories/kotlin-extended-clients/ https://www.christoph-sens.com/success-stories/kotlin-extended-clients/ Mon, 03 Aug 2026 00:00:00 GMT AWS offers extended clients for large SQS and SNS messages for Java only. The Kotlin counterpart: around 730 lines instead of thousands, no Jackson, tested and on Maven Central. https://www.christoph-sens.com/success-stories/pdf-generation/ https://www.christoph-sens.com/success-stories/pdf-generation/ Fri, 14 Jun 2024 00:00:00 GMT A microservice renders multilingual PDFs from HTML templates. Templates and translations can be swapped without a deployment – using license-friendly building blocks such as OpenPDF and Noto. https://www.christoph-sens.com/blog/media-group-technology-switch/ https://www.christoph-sens.com/blog/media-group-technology-switch/ Fri, 19 Apr 2024 00:00:00 GMT How a large media group put its app development on a common technology base with Flutter and brought it in-house. https://www.christoph-sens.com/blog/screen-forms-from-configuration-files/ https://www.christoph-sens.com/blog/screen-forms-from-configuration-files/ Fri, 19 Apr 2024 00:00:00 GMT Generating screen forms, including their REST integration, automatically from configuration files – a success story from an Angular project. https://www.christoph-sens.com/blog/the-role-of-signals/ https://www.christoph-sens.com/blog/the-role-of-signals/ Fri, 19 Apr 2024 00:00:00 GMT Why Angular introduced Signals and how they differ from Observables.