As a startup CTO, every engineering hour is precious. Build the wrong thing and you burn runway. Buy the wrong tool and you inherit someone else's limitations. Here's how to make this decision systematically.
The Core Question
Ask yourself: "Is this our competitive advantage?"
If the answer is yes — build it. If no — buy it. This single filter resolves 80% of build-vs-buy decisions.
Always Buy (Almost Never Build)
- Authentication — Auth0, Clerk, or Supabase Auth. The security surface area is too large to DIY.
- Payments — Stripe. Period. The compliance burden alone would consume your entire engineering team.
- Email/SMS — SendGrid, Postmark, Twilio. Deliverability is a full-time job.
- Analytics — PostHog, Mixpanel, or Amplitude. Instrumenting is your job; building the analytics engine is not.
- Monitoring — Datadog, Sentry, or Grafana Cloud. Focus on fixing bugs, not building dashboards.
Always Build (Almost Never Buy)
- Your core product logic — The algorithms, workflows, and business rules that make your product unique
- Your data model — How you structure and relate data is a competitive moat
- Customer-facing UX — Your interface IS your product. Don't let a template define your brand.
The Gray Zone: Use This Checklist
For everything in between, score each dimension (1-5):
- Differentiation — Does building this create competitive advantage?
- Complexity — How complex is the domain? (Higher = favor buy)
- Customization — How much do you need to deviate from standard behavior?
- Integration depth — How deeply does it need to integrate with your core?
- Maintenance burden — What's the ongoing cost of owning this?
The Hidden Costs of Buying
Every SaaS tool you add creates vendor dependency, API integration maintenance, and a new failure point. At 20+ tools, the integration complexity becomes its own engineering problem. Be deliberate about what you bring in.
Building an MVP and need to make smart trade-offs? We help startups ship fast without cutting the wrong corners.
