Vincent Castelluci

With the success of the payment middleware solution we designed earlier, we went on a journey to make it an independant and bankable SaaS. This was an inspiring and rich journey, which taught me that this is no small task to drift from in-house solution to market-sellable software. An impactful choice had to be taken after an issue related to the core paradigm of the product was discovered: we were still sensitive to partners' instability. I suggested and led the switch towards a much more stable solution, designed for this purpose: Spring WebFlux. This was full of challenges: a new paradigm for the whole team, very few frameworks available at that time, many use cases were not handled and had to be developed locally, but we knew this was the right solution, so we did it and overcame all those challenges. From just an API contract, we delivered a product which was: - sellable outside of the company (and was sold) - profitable - even more robust - failsafe - observable - extendable Amongst the whole bunch of new technologies we used, the most notable and impactful were: - Project Reactor: this is a crazy awesome technology, and has been the main tool for our redemption (and no, Loom will not make Java's reactive technology obsolete at all) - OSGi: another splendid framework which allows feature extension at runtime using plugins; this was a must have for our product, avoiding even simple instance restarts when adding new features - OpenTelemetry: this has played a huge role in our tweaking and debugging process, and without it, in a reactive context, we might have had difficulties to pinpoint issues Apart from this main mission, I had the chance to design and deploy solution all alone, such as in-house PSP and an pay-per-use billing project, for which I am very thankful to Decathlon for trusting and believing in me, leaving me the chance to choose the best technology to tailor the best solution for them.

Ideally looking for a challenging mission in fields I am not yet comfortable with or I don't even know, with high expectations on quality and results.

My main mission was to improve, support and maintain the centralised payment middleware as well as integrate it on the European Decathlon website. The team size for the middleware was of 7 people (but more than 50 for the whole website) which I could call friends, as we not only worked together but shared the same goal for our product. When I arrived, we were starting to move toward agile methodologies and it has been a long and interesting voyage, with no end as continuous improvement was and still is our motto. The technical stack was (mostly) : - Java 7 then 8 - Tomcat - Spring MVC - Hibernate - Oracle Database (which was imho a bad choice) - Maven - Jenkins - SVN then Git - RedHat - Rundeck (which was imho a bad choice) - Bash and Python - JavaScript - HTML - CSS - FreeMarker - GitLab and its pipeline - Docker - Flyway After two years, I was offered the opportunity to become technical leader, which I accepted as a new challenge. My main tasks was then to : - improve quality of the payment perimeter through code reviews, tests, spreading best practices, upgrading frameworks and API... - train newcomers to be operational as quickly as possible by redacting documentation on processes, plan training, pair programming and mob programming sessions - open the application source (which is not as easy as it seems as it points out many flaws, severe or minor) - make the application more robust and resilient by adding stress tests, measure health and plan emergency solutions in urgent cases What I learned thanks to this mission : - Quick & Dirty solutions needs to be instantly followed by a solid solution - BDD, which translates as TDD for the developer is a must have for each feature if you want to be able to react quickly later on - sometimes, agile, extreme programming or other trendy methodologies can make you loose time for an insignificant gain (or even loss) of organisation - success on a project is not achieved without human

Différents petits projets visant la montée en compétences sur les outils du quotidiens du développeur (outils de build, API, frameworks,...)