Coinbase Software Engineer Interview Experience — Three OAs, a Block-Mining Coding Round, and Two AI-Assisted Rounds

I heard Coinbase had layoffs today. Not sure how that'll affect hiring. Sigh, hope everyone's okay. The people I dealt with, including HR, were all really nice.

Sharing my previous interview experience — the whole process.

HR reached out asking if I wanted to interview with Coinbase (I'd applied 4 years ago but never went further in the process — they might still have had my info), so I went ahead and interviewed.

First there were three parts of OA.

OA1 was like a GRE-style test, 50 questions in 15 minutes — GRE-style sentence completion / the closest-matching-image type questions from Chinese civil service exams / plus basic math. I'm strong at this and finished all of them. It only counts the number you got right.

OA2 was a personality/tendency test, pretty long, almost 200 questions. Just pick the answers that show you're hardworking and grinding it out.

OA3 was an AI coding round — you had to write the jump boundary function for a Flappy Bird. Their system had a frontend that rendered a simulated map. You use AI to do it (though it's not that smart). I passed 16/20 tests but still passed overall.

The onsite (VO) was 4 rounds spread across three days.

One coding round on block mining — really hard, the problem was hard to understand, if you've never mined crypto you basically can't understand it. The first question went fast but the second one had dependencies that were also hard to code. The problem was pretty vague, no input/output given. The interviewer didn't give input/output at first, but the backend actually had it. In the end I got it running but with a bug. Roughly it was: greedily pick by fee/size ratio, then DFS to find dependency paths, gather them all and calculate together — some had parents, some didn't. The problem was really hard to understand.

One AI Coding round had four parts, the questions were kind of like that mock OOD database cursor query thing: 1) find a bug, 2) talk through how you'd build a new feature, 3) PR review, 4) production debugging. The guy was really nice, you just had to talk with him and produce answers based on the responses AI gave you. He'd record how you used it, and you had to share your screen.

One system design round — design a crypto order placement flow, but the matching is done by a third party, and there can even be multiple of them, which I wasn't too familiar with. The interviewer felt like they really knew their stuff and basically hit the key points. My domain knowledge here was limited, especially not knowing what connection protocols the exchange supports. Some things, like large-scale order placement, I didn't answer that well — basically gave a workable-ish solution.

One BQ round with the hiring manager from a neighboring team, standard questions. They also asked how I use AI day to day. It wrapped up in a bit over 30 minutes.

Job hunting is too hard. Hope everyone's doing okay.