A vendor wanted a per-scan fee to read license plates at a condo gate. I replaced them in a weekend, and the rest of the app never noticed.

That last part is the whole point.

The gate-access product talks to a plate reader through a single interface. Give it an image, get back a plate. Whether that's a commercial API or a self-hosted open-source model behind the interface is a detail the rest of the system is deliberately blind to.

So swapping the paid vendor for a self-hosted OSS reader was a contained change: new adapter, same contract, zero downstream edits. Recurring cost went to roughly zero. Image bytes stopped leaving the building, which the residents care about more than the invoice.

This is what vendor lock-in actually costs teams that didn't design for it. A swap that should take a weekend becomes a quarter-long rewrite because the vendor's SDK is wired through 40 files.

Founders feel this bill every month. The fix is architectural, and it's cheap if you do it on day one.

Want to see how I structure swappable providers so no integration is load-bearing? Ask in the comments.