## Problem / Use case

You want to monitor Real User Monitoring (RUM) `longtask` durations and categorize them into performance buckets (e.g., fast, moderate, slow) to track client-side performance issues by severity.

## Query

```dataprime
source logs
| filter cx_rum.longtask_context.duration > 0
| groupby case_lessthan {
   cx_rum.longtask_context.duration:num,
   100 -> 'Green (0-100)',
   200 -> 'Orange (101-200)',
   300 -> 'Red (201-300)',
   _   -> 'Purple (301 - *)'
 } as Range
 agg count() as count
```

## Expected output

| Range             | count  |
| ----------------- | ------ |
| Green (0-100)     | 143973 |
| Red (201-300)     | 14961  |
| Orange (101-200)  | 36519  |
| Purple (301 - \*) | 6230   |

## Variations

- Adjust bucket thresholds based on your UX performance criteria.
- Swap `count()` for `distinct_count(session_id)` to measure impact per user session.

## TL;DR

Use `case_lessthan` to bucket `longtask` durations into performance ranges for easier trend analysis and alerting. Think of it as your RUM-grade Energon scanner.