Square is Square, expect the hiring process to take a while and have a few rounds. It helps if you're recruiting at other companies to put some soft pressure on them to move forward. But if you put too much pressure, as I suspect I did, they'll pass. The interview process itself was legit and thorough. No brain teaser questions were asked, mostly skills and knowledge based. I claimed to be fairly proficient with PSQL, they made me solve a couple of problems on the spot to make sure I wasn't bs'ing. Nothing too crazy, but you should know about joins, left joins, grouping, ordering as well as a little bit of theory on how the relational database systems work. I met with 10 different people, including the VP of product, so they do take their hiring seriously and each of them asked thoughtful, practical questions. As a caveat, people did seem sort of worn down and beat up by the work environment at Square so you should know that you're probably signing up for super crazy work hours.