When should a startup build custom infrastructure?
A framework for deciding when to build versus when to buy.
The default answer should almost always be buy, not build — every hour spent on infrastructure that isn't your product's core differentiator is an hour not spent on the thing customers actually pay for. But "almost always" isn't "always," and knowing the exception matters.
Build where it's your actual edge
Build custom when the infrastructure IS the product's edge — the thing a competitor genuinely can't replicate by paying for the same vendor you would. Buy everything else: auth, payments, email, hosting, observability. These are solved problems with mature vendors, and reinventing them is rarely where the startup's advantage lives.
Watch for the 'interesting problem' trap
The failure mode to watch for is building custom infrastructure because it's technically interesting, not because it's strategically necessary. That's a trap smart engineers fall into more than anyone else — ask what the business actually needs, not what would be a fun system to design.
Revisit the decision as you scale
A vendor that's the obvious choice at ten thousand users might become the wrong economic tradeoff at ten million. That's fine — it's a decision worth revisiting deliberately when the numbers actually justify it, not a reason to build custom from day one on the assumption you'll need it eventually.
- Default to buying infrastructure — build only where it's your actual competitive edge.
- Auth, payments and hosting are solved problems; don't reinvent them.
- Watch for building things because they're interesting, not because they're necessary.
Building an MVP that doesn't need to be thrown away
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