Cartesia interview prep

50 Algorithm & Systems Problems

This set is built around Cartesia's real-time voice pipeline — streaming audio in and out over a socket, low-latency speech synthesis and transcription, and the session/connection management that holds a live call together — plus common infra patterns any team serving models under tight latency budgets needs. Problems are ordered by relevance, not just difficulty: the first 17 model scenarios straight out of streaming voice systems (ring buffers, jitter buffers, barge-in, backpressure); the next 17 are adjacent infra patterns (routing, caching, scheduling); the rest are classic medium/hard algorithm categories given a light Cartesia-style framing.

How to read the grounding badges: every problem page states plainly whether its scenario is Confirmed — a pattern that directly reflects how a real-time streaming voice system like Cartesia's has to work — or General Pattern — a plausible, industry-standard scenario that is a general infra/algorithm pattern rather than a confirmed detail of Cartesia's actual implementation.

What's on each problem page

  • The scenario, framed around Cartesia's real-time voice/infra domain, with its grounding badge.
  • The actual stub function signature and docstring from the corresponding .py file in ../ (the code you'd run locally to practice).
  • A step-by-step walkthrough of the solution approach — the reasoning, not just the final code.
  • A "how to recognize this pattern in general" section, for transferring the approach to a novel problem in an interview.

Running the code yourself

Every problem has a matching pair of files one level up, in cartesia-coding/src/:

src/1_ring_buffer_audio_chunks.py            # stub — implement the function, then run it
src/1_ring_buffer_audio_chunks_solution.py   # reference solution — run it directly

python3 N_slug.py runs your implementation against the built-in test cases and asserts they pass. python3 N_slug_solution.py runs the reference solution and prints a step-by-step trace of its execution.

Start with Problem 1: Fixed-Capacity Ring Buffer for Streaming Audio Chunks, or jump to any problem from the sidebar.