# One slow step that blocks the rest

Prompt · Performance and scale · P08

Finds one slow step that makes every other request wait in line behind it.

## Prompt

```text
Find synchronous work performed in latency-sensitive asynchronous handlers, including filesystem operations, parsing, compression, large serialization and CPU-heavy transforms. Measure event-loop impact and identify safe offloading, batching or scheduling fixes.
```

**What it returns:** Event-loop delay or long-task measurements tied to the specific handler.

**Skip it when:** Background scripts where nothing else shares the process.

**Tools:** Node profiler or the browser's Performance panel.

**Changes:** Changes nothing

**Sessions:** One session

## Related

- [Slowest journeys, end to end](https://www.atlasscope.dev/prompts/slowest-journeys-end-to-end): Shows where the seconds go on the paths people actually use.
- [Work repeated for nothing](https://www.atlasscope.dev/prompts/work-repeated-for-nothing): Finds work redone on every request or screen redraw when nothing it depends on changed.

Source: https://www.atlasscope.dev/prompts/one-slow-step-that-blocks-the-rest