Glossary
Brownfield and greenfield
Greenfield means building on an empty site. Brownfield means building while an existing system keeps running around you.
The difference is not technology, it is constraints. On a greenfield you decide freely. On a brownfield you decide against existing data models, live contracts and users who did not order a migration.
Almost every commercially interesting project is brownfield. Greenfield mostly exists at the start of a product or in a clearly bounded niche beside it.
How you notice it
- A system is live and earning money.
- Requirements exist mostly in the running code.
- Every change has to work around what is there.
Frequently asked
Why do brownfield estimates go wrong so often?
Because the unknown part dominates. Greenfield effort scales with the requirements, brownfield effort scales with what nobody documented. Two weeks of reading the existing system before estimating changes the number more than any technique.