Konstantin Borovik
Software Engineer | AI & LLM Engineering | lab5.ca
insightsBuild-vs-Buy - the 90/10 software rule small businesses can use
There's a rule going around among AI-native operators, cleanest version from SaaStr (a media company reportedly run by about three people and a couple dozen AI agents): buy 90% of your business software off the shelf, and build only the 10% where no tool fits. Don't try to out-build Salesforce in a weekend. But the slice that's genuinely yours — the workflow that drives your business, the one no vendor sells — build that.
The split isn't new. Good engineering leaders have always bought commodity software and built only their differentiators. What's new is who gets to follow it. For decades the custom 10% was a luxury good — months of work from six-figure engineers, hundreds of thousands of dollars before anything shipped. Big companies funded it; a 40-person distributor or a regional clinic couldn't. So small businesses bought 100% off the shelf and bent the business to fit a tool optimized for the average customer, which is nobody's actual case.
AI didn't change that by writing flawless software. It doesn't. It removed the grunt work — scaffolding, boilerplate, glue code, test stubs — that made building the 10% headcount-intensive. The cost of that custom slice fell by roughly an order of magnitude, so one capable, AI-fluent developer now covers what a team's budget used to. And one such developer is something a small business can finally afford.
The catch is worth stating plainly: letting a model generate unsupervised produces slop — code that demos well and breaks in production. An MIT study found ~95% of attempts to put generative AI into business processes show no measurable return. The barrier that fell is writing the code; making it grounded, capped so a bug can't run up a fortune, and instrumented so you can see where the money goes is a separate discipline. That's the part I build around — and the honest boundary holds: if the work needs a standing team, that's work for a team, not a thing to fake with one person and a model.
The test for everything else: is running this product someone else's full-time job? CRM core, payments, auth, accounting — keep buying. The custom 10% is for what's specific and differentiating to you. I built MailPilot as my own checkable receipt: a production AI agent that reads an incoming email, searches a knowledge base, and replies with a sourced answer in under a minute. The code is open, every model call is traced, and you can email the agent yourself and watch what it does.
Read the full post: https://lnkd.in/gzeXJk-z