The build versus buy decision comes up constantly in software development. Should you build your own authentication system or use an existing service? Write your own email delivery layer or integrate a provider? Implement your own search or use a hosted solution? The stakes are real — the wrong answer can mean months of work on something that was never a competitive advantage, or it can mean handing over control of something critical to a third party.
The Core Question
The fundamental question is whether the capability you are considering represents a differentiator for your product. If customers choose your product because of this capability — if it is part of what makes your product unique and valuable — then building it gives you control, flexibility, and the ability to make it genuinely excellent. If customers do not care who provides the capability, only that it works, then buying is almost always the right answer.
Authentication is a good example of a clear buy decision for most products. Users do not choose your product because of your login system. They care that it works securely and reliably, and established providers can deliver that better than most teams can build it in-house.
The Hidden Costs of Building
Building custom solutions for generic problems has real costs beyond the initial development time. Every system you build, you must maintain. You must handle edge cases, security vulnerabilities, performance issues, and the operational burden of running it in production. For capabilities that are not core to your product, these ongoing costs are rarely worth the investment.
The Hidden Costs of Buying
Third-party dependencies are not free either. They introduce vendor risk — what happens if the provider raises prices, changes terms, or shuts down? They can limit your flexibility, particularly if the integration becomes deeply embedded. And the integration work itself is often more substantial than it first appears.
The right answer balances these considerations honestly. We lean toward buying for infrastructure and generic capabilities, and toward building for the core experiences that differentiate the product. But every situation deserves its own analysis.