Luc D.

Pennylane is a French financial platform combining accounting software and management tools. It connects accountants and businesses through a shared system, centralizing invoicing, expenses, and real-time data. The architecture is based on an API-oriented monolith and asynchronous processing (background jobs).

I joined Pennylane as a Senior Backend Engineer in the IAM squad (authorizations and permissions), initially as the sole senior in a newly created team, within a monolith of over 300 developers. The environment was highly structured: advanced CI, strict Git hooks, CODEOWNERS, and clear organization (Junior to Staff, EM, PM).

My main mission was to design and lead a new permissions system based on CanCanCan, replacing a legacy solution that was difficult to maintain. I defined the architecture, developed key features, and ensured integration into the monolith, with strong constraints on data migration and consistency. I collaborated with multiple teams to ensure smooth adoption and a scalable foundation.

I also contributed to cross-functional topics (Sidekiq) and used advanced tools like Datadog, Sentry, and AI solutions (Claude, Dust) integrated into the workflow.

This experience confronted me with the challenges of scaling a monolith: Packwerk for code ownership management, merge queues, inter-team coordination, and strong quality constraints. I strengthened my Ruby/Rails expertise and my ability to lead complex projects there.

Through the global network Proxify, I’m currently working with Faktus — a fast-scaling company that uses cutting-edge technologies to act as a financial intermediary between various entities in the real estate market.

I work with the latest versions of Ruby, Rails, and Sidekiq, as well as Turbo and Stimulus, in a fast-paced environment. The team is still human-sized, which gives me the opportunity to contribute across the board. My focus is on building new features while actively managing and reducing technical debt. We are also relying on Active Admin.

A key part of the business involves integration with a third-party Banking-as-a-Service provider — an area in which I’ve now built strong expertise.

The environment is dynamic and stimulating. I’m enjoying working with modern Rails tools like Turbo and Stimulus, and I strive to bring both professionalism and my startup experience to help the team grow efficiently.

During my collaboration with Welligence, I worked as a Data Engineer on a tool built for internal data scientists. It was used to scrape and inject data into multiple PostgreSQL databases, as well as generate various reports in PDF and Excel formats.

The role had a strong coordination aspect. Welligence is a U.S.-based company with developers across Europe and Vietnam, and each global economic region had a head of data relying on the tool and working on a different time-zone. This required effective communication skills and experience with Ruby on Rails, Jenkins, Sidekiq, and some Python.

As the company scaled, we faced several reliability and performance challenges. One of my key contributions was building a GeoJSON import feature to visualize oil field shapes on a 3D globe.

While the experience was valuable, the role became increasingly support-oriented, with limited opportunities for hands-on development. I decided to move on in search of a position with a stronger focus on software engineering.