Why would €42k not a fair wage? Looking at INSEE data, the median salary in France is €38409, 42k-50k to write API endpoints seems fair to me, what do you think would be appropriate?
You say you have a shortage for API devs?
Then either:
1) pay more at which point you'll be flooded with aplicants and if not then you have a real claim for skill shortage with the government and can secure visas for immigrant workers or
2)train them yourself, there's plenty of motivated people of all ages willing to learn something that's in demand. Simples.
But what's that?! Investing in the workforce is too expensive for the shareholders?! Boo-hoo, my heart bleeds for the poor companies and their offshore accounts.
Whether you want to keep that is another thing in itself. From what I see, the availability for large amount of beginners (Not necessarily foreign, see bootcamp) does not affect the market value for experienced programmers at all.
That’ll be great for the world, but not for us — it’ll make this argument about €50k/year salaries depressing our wages seem bizarre to future generations.