He probably has a very good understanding of the company's priorities and politics. Pay more attention to that. Politely disagree on the tech side when you thin

He probably has a very good understanding of the company's priorities and politics. Pay more attention to that. Politely disagree on the tech side when you think it's appropriate, make your arguments, and then implement based on what comes out of that. On stuff like JSON vs. custom delimiters, that's old thinking - you can probably win that argument by finding out exactly why he thinks that way. Chances are that he's concerned about bandwidth overhead or something similar, or he's thinking about the effort of implementing it from scratch. You can argue against the former by doing some tests with your webserver's mod_gzip, and the latter by coding up a POC with a JSON library and showing him how easy it was. Being mentored doesn't imply that you have to take everything they say as gold. Approaching their advice with a critical but respectful attitude is probably best.