parallel run
B1CEFR level
25/100Rarity: fairly common
TechnicalRegister
Operating the old and new systems side by side to prove the new one before the old is switched off.
We'll do a month's parallel run on payroll so nobody's salary depends on untested code.
Rarity runs from 0 (a word everyone knows) to 100 (almost never seen outside specialist or literary writing). Level is the word's real difficulty on the CEFR scale, from A1 to C2.
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