Anthropic Software Engineer Interview Experience — Call Stack Sampling and GPU Weight Distribution System Design

I interviewed this past Thursday.

The first question was: given continuous call stack samples, generate timestamped function start/end events. While I was answering, the interviewer kept pushing back with follow-up questions, including things like:

• How do you compute the change between adjacent call stacks using the longest common prefix?
• Why do end events go from inside out, while start events go from outside in?
• How do you distinguish between recursive calls to the same function name?
• A function only counts once it's appeared n times in a row — how do you maintain that state?
• If the samples come in as a streaming input, how do you avoid keeping the entire history?

For the system design part, I had to design a platform for shipping tens to hundreds of GB of model weights out to a large number of GPU workers. My interviewer mostly cared about:

• How do you get observability when node capacity is opaque or a deployment gets stuck?
• How do you guarantee that requests only get routed to instances that have fully loaded the correct version?

Still waiting on the result.