A technology choice defended with "it is what we know" is sometimes right and never checkable. A proof of concept makes it checkable — but only when it is run as a decision procedure, and not as an early version of the product.

00 / A proof of concept is a question with a deadline

Three things separate it from a prototype: a question whose answer is allowed to be no, a criterion agreed before anyone writes code, and a date on which it ends. Drop any one of them and the PoC quietly becomes the first version of the system — the demo ships, nobody re-reads the question, and the stack has been chosen by sunk cost.

The question has to be able to fail. "Can we build this in X?" cannot: the answer is always yes, given enough time. "What does X cost us on the part we are actually worried about, in two days?" can.

01 / Make the comparisons comparable

Same task, same timebox, same reviewer, and the criteria with their weights written down before the first commit.…