I would expect that to be called tech lead. Though probably closer to 80/20 (or lower) than 90/10 by the time you include all the extra work and meetings he or

I would expect that to be called tech lead. Though probably closer to 80/20 (or lower) than 90/10 by the time you include all the extra work and meetings he or she has to go to by dint of being in that role (vs say the next most senior engineer).