# Interview Scenarios

This starter is annotated reading material and the source of truth for the lab preview. Running anything is optional; the reading goal is to explain the mechanism without hiding behind a framework call.

## Reading focus

Practice explaining a parallelism choice with problem, mechanism, communication, tradeoff and measurement.

## Annotated sketch

```text
## Answer template

1. Problem: what does not fit or scale?
2. Mechanism: what is replicated or sharded?
3. Communication: which collective appears?
4. Cost: memory saved versus bandwidth/latency added.
5. Measurement: what profiler or metric confirms it?
```

## What to explain

- problem states the bottleneck.
- mechanism says what is sharded.
- measurement says how to verify.

## Common trap

- Do not recite DDP/FSDP/TP/PP without dataflow.
- Do not ignore optimizer state and activation memory.