Comparison
Build versus buyvsNot invented here
Build versus buy
you costed six weeks to build it and nobody costed the years of owning it afterwards.
The decision to write something yourself or to adopt something existing. The comparison is almost always done wrong, because building is costed as the initial implementation while buying is costed as its whole lifetime; the honest version compares total ownership on both sides, including operations, upgrades and the people who will leave. The usual tiebreaker is whether the thing is core to what your business is actually good at.
Full entry →Not invented here
the team wrote its own scheduler because the existing one did not fit exactly, and now maintains a scheduler.
Rejecting external solutions in favour of building your own, usually justified by a genuine but minor misfit. The build is systematically undercosted because the ongoing ownership — bugs, upgrades, documentation, the person who leaves — is not counted at decision time. The mirror-image trap is real too: adopting a dependency for something that would be forty lines is its own permanent cost.
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