Anthropic Senior+ Software Engineer Interview Experience — An Extra LRU Cache Round After Admitting I'd Seen the First One Before

Overall the questions weren't hard, but there was a lot of code to write.

The phone screen was one coding round — they asked the file deduplication problem (Q2), done in Replit.

The onsite ended up being 5 rounds total; it was originally supposed to be 4, and they added one more later:

• Round 1 (Coding): asked about the web crawler problem (Q1). The interviewer asked if I'd seen a similar question before, and I honestly said yes — which foreshadowed the extra round they tacked on later.
• Round 2 (Hiring manager): just asked basic questions.
• Round 3 (Culture interview): asked questions related to AI safety.
• Round 4 (System design): another question that's been floating around here before, asking about designing a GPU inference API.

After the interviews, the feedback was positive, but the recruiter told me they were adding one more round on short notice — they said the onsite coding round was "inconclusive" because I'd said I'd seen a similar question before, so I ended up doing another round with a completely new question.

The new question was how to implement a Python LRU cache. They give you an LRU cache that's already implemented, but it doesn't handle Python's variable-length arguments and keyword arguments properly, and you need to add that. The follow-up was how to make the LRU cache persistent. I spent a huge amount of time on serialization in this round, and in the end my code didn't run. I originally planned to use pickle, but the interviewer said I didn't need pickle — I could just hand-roll the serialization/deserialization with JSON 😭 — and then I never finished the follow-up. Looking back, I should have just stuck with pickle so I could focus on the core logic.

Overall it was pretty tightly packed — the questions weren't hard, but there were a lot of traps to fill. After finishing the four onsite rounds, the recruiter started talking about the package. Anthropic offers apparently aren't negotiable, and if you don't count the paper money, the comp is far below FAANG. They also seem to lowball your level — I interviewed for staff, but the recruiter said they could only give me the internal level equivalent to senior, not staff, explaining that their internal leveling is "FAANG minus 1."