Build · Buy · LLM
the decision, visualized
07

It's not either/or. It's a stack.

Real products use all three options. The useful question is which layer gets which option. Here is one example stack, a payments product. Switch eras to see which parts moved. In this example, 6 of 14 parts changed approach between 2022 and 2026.
Click any part for the reasoning
Build
Buy
LLM
Experience
Core domain
Fuzzy edges
Operations
Commodity
Graduation paths: decisions aren't permanent
LLMBuildBuydistillspec is stable, volume grewrules exploding into edge casesinsourceseat bill > an engineerit became commoditydashed = paths AI made cheaper · prototype with a model, keep the core, re-check vendors every renewal
  • why it mattersMost of the movement happens in the middle layers: the fuzzy edges and operations. The core domain and pure commodity barely moved.
  • why it mattersSeveral of the parts that moved left a vendor. When a vendor's value was glue plus a UI over a rules engine, a model or a coding agent can now replace it.
  • why it mattersSome parts moved from Build to LLM. Brittle parsers and rules that kept growing with edge cases are a good fit for a model with deterministic checks behind it.
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