La Tienda del Pintor
A custom payment gateway against a local bank for La Tienda del Pintor, a paint supplier selling in soles, built because no processor had done it for them.
For three years I was the only developer on La Tienda del Pintor's e-commerce, a paint supplier selling in soles. That meant the job was never only the code. It was gathering the requirement, choosing the approach, deploying it, and then answering the phone when something broke on a Saturday.
Most of that work was the ordinary substance of running a store: a custom theme, technical SEO, performance, and the REST APIs behind them in Node and Express. One piece was genuinely custom software.
Why the plugin had to be written at all
WooCommerce has a plugin for almost everything, and that is exactly the trap. The global processors have polished, maintained, documented WooCommerce plugins. A regional bank has a specification and an integration team, and whatever you need on top of that you write yourself. The choice was not between a custom plugin and an official one. It was between a custom plugin and telling the client their customers could not pay with the method those customers actually used.
So I built the payment gateway against the bank's own specification, a custom plugin nobody else had written because nobody else needed exactly this bank.
The part that generalizes
Working directly with the business owner rather than through a product manager changes what a requirement is. Nobody hands you a spec. They tell you what is going wrong with their day, and turning that into a technical decision, including telling them when what they asked for is not what they need, is most of the value you provide.
That is also where the maintenance discipline comes from. Everything I shipped here, I was going to be the one supporting. It is a fast way to learn that clever is expensive and boring is cheap.
A note on detail
The plugin code belongs to the client, so there is no repository to link and I will not reconstruct implementation details from memory into a page that reads like documentation. La Tienda del Pintor is still trading on WooCommerce today, which I am glad about.
If you want the specifics, the bank's integration flow or how the store was kept fast, ask me and I will walk you through it properly.