Hullo there! I’m Rémi Mercier.
I’m a freelance software engineer, a writer, and a former stained-glass maker (yep).
Main occupation: software engineer
I’ve been a professional developer for the past eight years, and I’ve worked in tech for twelve years. Before being a professional programmer, I worked in product and marketing for startups for four years. Before that, I held an awful lot of jobs, mostly in non-tech (albeit very nerdy) fields for 15 years.
I define myself as a product engineer: someone who's good at the intersection of tech, business and humans.
Are you a small to mid-sized team? Are you struggling to get your roadmap done? Head over to the page dedicated to my retainer offer. I’m currently working with small to mid-sized teams to help them ship Rails applications that generate 6-figure revenues.
Right now, I’m actively working on the Ruby Stained Glass project where I build limited-edition stained-glass panels celebrating our beloved language, Ruby.
Writing
I run this website where I share what I learned while building software. It’s my way of giving back to the community.
I focus on making things as simple to understand as possible: real-life examples, step-by-step tutorials, expressive naming, etc… No def foo = @bar shenanigans.
I mostly write about Ruby and Rails, testing (with both RSpec and Minitest), debugging, PostgreSQL, and how to deliver big features without losing your mind. I also write about careers in tech, marketing, and the Ruby Stained Glass project.
Since 2018, close to 60,000 readers have spent time on my corner of the internet. My posts are often featured in Ruby Weekly, HN, etc…
My top 3 articles are:
- Exploring dependency injection in Ruby (~8k views)
- Build a minimal feature flags manager in under an hour (~5k views)
- Introduction to Git Bisect: travel through time and bugs (~3k views)
Newsletter
My general newsletter is a good way to receive my new posts before anyone else. We’re currently closing in on 500 subscribers from all over the world!
I’m still looking to make it a more creative space. This will probably evolve as I explore new ways of supporting my writing work.
I’ve also been running a pop-up newsletter since May 2026 called the Ruby Stained Glass Notes through which I share my progress on building limited-edition stained-glass panels celebrating Ruby.
Drawing, design and art stuff
Drawing has played a big part in my life.
When I was 14, a teacher suggested I study design and applied arts. He had spotted me drawing caricatures of my schoolmates instead of taking notes.
Design has taught me a few important lessons:
- How to formulate a problem so it’s understandable.
- There are many ways to solve a problem.
- How to clearly articulate my thoughts.
- Better done than perfect.
A few arty things I like a lot: Romanesque architecture, stained glass (obviously!), generative art (Matt Deslauriers ❤️)…
I also enjoy building things with my hands: some low-key woodworking, anything that could come up in restoring an 18th-century house (and let me tell you, A LOT can come up!).