If you go by the wikipedia entry that comes up when searching for premature optimization, there is no established word yet.
This means it is a "Fachbegriff" which originated in a foreign language and should be used. In this case your colleague/friend should search for premature optimization.
The standard translation "verfrüht" does not have the same connotations.
Premature means before it is ripe or mature(d).
So in extend it means you should let something (the codebase) ripe and or settle
before you spend/waste time optimizing it prematurely.
Then be the best German translation I can come up with would be:
Verfrühte Optimierung unreifer Software.
As you can see it is a sentence and not just two words.
So in my opinion the english original is superior because it expresses the same sentiment more briefly.
If you insist on using German words only I'd say stick with "Verfrühter Optimierung".
- Or "Vorzeitiger Optimierung". (almost the same as premature)
- Or "Vorreifer Optimierung" (pretty much the same as premature, unusual but possible)
I checked in Google and the results, using "Verfrühte Optimierung" look promising. The first entry is exactly about this topic. 87.000 Results are not to shabby either.
Google: verfrühte optimierung
If you search for "verfrühte optimierung" there are still 244 results left. Some of them point to the english original phrase.
"Optimieren 24.1.3 The root of all evil "Premature optimization is the root of all evil""
Google: "verfrühte optimierung"
Google: "Vorzeitige Optimierung" beats that with 1020 entries.
Google: "Vorreife Optimierung" only returns this very page you are reading.
Google: Vorreife Optimierung results in some nice non IT-Specific results for this concept. Like unripe food and how to let it mature before processing it. (An already invented wheel?)
Other examples for borrowed words "Fachbegriffe" in the IT-space are:
- Personal Computer
You could search for elektronische Nachricht/E-Nachricht or Netz-Seite/Netzpräsenz. If you are intent on looking for German phrases. But again they are not the originals and are less common.
It might take some time before the word(s)/phrase are assimilated and Germanized and for example something like Courier --> Kurier happens.
Until then. Stick with the most popular expression for research.