I graduated with a MSc and now I'm working my first job. Everything was fine until this year when I asked to renegotiate my salary. I asked for 35% to compete with inflation and compensation for all the new responsibilities I picked up during my 18 months there. I had to settle for 25% which was fine back then but my costs keep rising and after some more market research I've come to the conclusion that I'm still quite underpaid.
We are a small team of four developers with a very complex domain with ancient legacy code. Training a new engineer (if you can find one) will take about a year to reach the domain knowledge I posses. While I was hired as a junior my current set of responsibilities puts me between medior and senior level for this company.
I also recently found out that I'm paid about 2000 euros per month less than my colleague (25y experience) and about 1000 euros compared to market rate for my area.
We do the same work I work without supervision and my work is not inferior to theirs when you compare code reviews.
So should I be paid equally compared to my colleagues?
P.S. I do really like my job but leaving this much money on the table is going to breed resentment.
EDIT: Because our team is so small it would likely affect plans for the following year as the one remaining senior would have to spend his time training staff.