Build vs buy: should you build your own experimentation layer?
The first A/B testing prototype is a weekend of work. The real bill comes later. An honest look at the build vs buy decision in experimentation.
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At some point every engineering team considers building its own experimentation layer. "We just need to split traffic and measure conversions, how hard can it be?" And the first prototype, honestly, isn't hard. The problem shows up later.
This is an honest look at the build vs buy dilemma. Building has real advantages, but the total cost is usually far above what it seems at the start. It's worth doing the math before you decide.
What looks simple at first#
Splitting users between two variants and counting conversions is a weekend of work. That's why many teams start there, convinced that maintaining it will be just as cheap.
The reality is that the hard part isn't the split: it's everything else. Correct statistical significance, sample management, assignment persistence, a dashboard that marketing can actually use, integrations with the rest of the stack, and ongoing maintenance as the site keeps changing.
The real cost of building#
The cost of an in-house layer is rarely in building it, but in maintaining it and making it usable by people who aren't engineers. Every new experiment turns into a ticket for the dev team, and technical debt piles up.
The costs that usually get underestimated:
- Recurring engineering time, not just the initial build.
- Correct statistical rigor so you don't misread your results.
- A dashboard the business team can use without a dev sitting next to them.
- Integrations and their maintenance with CRM, payments, and data.
- Opportunity cost: the product engineering isn't shipping.
When to build and when to buy#
Building makes sense in very specific cases: experimentation requirements so particular that no tool covers them, or a scale where the per-use cost of a commercial solution far exceeds the cost of maintaining your own. Some large platforms are at that point.
For most teams, buying wins. Bixlow gives you the layer ready to go, with statistical rigor, a dashboard for the business team, and integrations, while keeping technical control through staging and a secure API. The team gets the best of building (control) without the cost of maintaining it.
Key takeaways#
- The prototype is cheap; maintenance and usability are what's expensive.
- Building only pays off with very particular requirements or extreme scale.
- Bixlow gives you the layer ready to go with technical control, avoiding the debt of maintaining it.
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