Tackling Technical Debt With Experiments

Let me bring you back in time to 2008, a time when Javascript was used very differently than it is today. If you’ve ever inherited a pile of technical debt in the form of an old and outdated framework, you’ll feel right at home with my story.

Back then, I was working on a team as a developer maintaining and adding new features to an online hotel search engine whose entire front-end was built on Scriptaculous. Yes, that Scriptaculous, the one that made everything on websites wobble, flash, fade, or slide with a single line of code which in turn was built on top of another legacy which was Prototype.js. It was all fun until it wasn’t. By late 2008, the world was moving away to jQuery, and so were we. But there was a big catch: our product was live, serving thousands of users, and every single feature depended on that old framework.

The technical debt was real. Even though we had a decent test coverage, every new feature we had to add felt like a game of Jenga, touch one thing, and something else breaks. Business kept on pressing for new features, but we were spending more and more time patching code and stress levels were visibly increasing. We all knew we had to migrate away from the imminent legacy, but the risk of breaking the entire application was terrifying.

The easy (and incredibly dangerous) option would have been a “big bang” rewrite, freeze all new development, rewrite everything in jQuery, and hope for the best. But we already witnessed too many teams in our industry crash and burn trying that. We needed a smarter way.

The Experiment Mindset: Data, Not Drama

Instead of a heroic rewrite, we decided to treat the migration as a series of experiments. Our guiding principle: no disruption to users, no surprises to the business.

Here’s what we did: