How the interviewer opens it
“Design a service that converts live meeting audio into captions with timestamps and speaker labels. It must handle people who speak at the same time.”
The prompt is vague on purpose. The first minutes are for you. Reduce the prompt to the core features and agree on the numbers before you draw.
What to clarify first
- Audio input and speakers
- Overlapping speech
- Scale
- Read and write mix
- Latency
- Accuracy and corrections
- Consistency and availability
- Retention and recovery
- Timestamp meaning
- Model choice and exclusions
The interviewer has the answers. In a SysRound round, Alex gives these answers, as a real interviewer does.
Scope of a strong answer
Core requirements
- Receive live meeting audio
- Show captions with timestamps and stable speaker labels
- Represent speech from people who speak at the same time
- Restore caption delivery after a brief connection loss
Usually out of scope
- Train new speech models
- Translate speech or produce summaries
- Identify speakers by their real names
- Capture audio from meeting devices
What interviewers ask about
- Caption delay and accuracy
- Future audio can change a word or reveal a sentence boundary. Viewers need useful captions before that evidence arrives.
- Speakers who talk at the same time
- One mixed audio stream does not preserve each voice separately. Similar voices and overlap make both words and speaker labels uncertain.
- Caption continuity after a failure
- Replay can change words and segment boundaries. One speaker can have final captions while another still has unfinished speech over the same samples.
- Capacity during demand peaks
- Recognition cost depends on audio duration and overlap. Caption delivery cost also depends on viewer count and slow connections.
Common mistakes
- Treats speaker labels as a direct output of any speech recognition model.
- Assumes one mixed audio stream always permits complete recovery of simultaneous voices.
- Omits the order between partial revisions, final captions, and explicit corrections.
- Uses network arrival times instead of audio positions for timestamps.
- Treats a final audio interval as complete for every speaker during recovery.
- Sizes compute from viewer count instead of audio duration and model cost.
The bar by level
- Senior (L5/E5)
- Defines the delay budget and per-segment revision rules. Handles overlap limits, stable labels, replay, and durable finals. Sizes recognition and caption delivery separately.
- Staff (L6+/E6+)
- Proves that replay preserves finals and unfinished overlapping speech. Defines measurable quality trade-offs, zone failure behavior, and overload limits. States privacy and recovery limits.