Buy when the capability is common and the vendor's maintenance burden is spread across many customers. Build when the need is specific to your systems, off the shelf options cannot fit, and you can commit people to maintain it for years. Most teams end up buying the core and building glue.
The questions that decide it
Is it a differentiator? Security rarely is. Scanning, identity and logging are needed by everyone, so there is little reason to rebuild them. A custom check that encodes your own architecture rules may be worth building.
Who maintains it? A script written in a week can cost a person a day a month forever. Detection rules go stale, APIs change, the author leaves. Price maintenance at a realistic share of an engineer's time, and name that engineer.
How fast do you need it? Buying usually reaches value in weeks. Building takes months before it matches even a basic product. If an audit or customer deadline is close, time matters more than fit.
How good is the fit? List your must have requirements and test them in a trial. A product that covers eighty percent and integrates with your workflow beats a perfect build that never ships.
Hidden costs on each side
Buying has costs people forget: integration work, tuning, training, renewal increases and the effort of leaving. Ask how data can be exported and what happens to your configuration if you switch.
Building has costs of its own: on call burden, security of the tool itself, documentation, and key person risk. An internal tool also lacks the external pressure that makes vendors improve it.
A simple scoring approach
Score each option from one to five on five factors: fit, time to value, total cost over three years, maintenance risk, and exit flexibility. Weigh the factors by what matters this year. Write down the scores. The act of scoring usually exposes which factor is actually driving the preference.
The hybrid pattern
A common healthy pattern: buy the platform, build small integrations and policies on top. For example, buy a scanner but write your own rule that blocks releases when a service handling payments has an unreviewed exception. This keeps differentiating logic yours while the heavy engine is maintained by someone else.
Revisit the decision
Put a review date on the choice, usually eighteen months out. Needs shift, vendors change and internal tools can be retired. Treat the choice as reversible and cheap to revisit.
Quick check
When does building make sense?
When the need is unique to your environment, no product fits, and you can fund long term maintenance with named owners.
What is the biggest hidden cost of building?
Maintenance. Keeping a tool current, secure and documented often costs more than writing it.
Last reviewed: 19 October 2026.
