## TL;DR

Bright Data's own concurrency guide gives a scale ladder: under 50 URLs just go sequential; 50-500 means concurrency 10-20 with a semaphore; 500-10,000 bumps to 20-50 with progress tracking; over 10,000 you chunk into batches of 1,000 and save intermediate results.

## Fix

1. Bright Data's own concurrency guide gives a scale ladder: under 50 URLs just go sequential; 50-500 means concurrency 10-20 with a semaphore; 500-10,000 bumps to 20-50 with progress tracking; over 10,000 you chunk into batches of 1,000 and save intermediate results.
   Expected: you can confirm this matches your situation.

## When to use

- You are setting up or using this Bright Data concurrency ladder feature.
- The symptom matches: match the band to your URL count instead of maxing everything.

## When NOT to use

- Unrelated Bright Data concurrency ladder issues (different feature, different failure).
- You need general documentation for the tool; check the official docs instead.

## Compatibility

Reported against Bright Data concurrency ladder. Source: https://github.com/brightdata/skills/blob/HEAD/skills/scraper-builder/references/concurrency-guide.md.

## Variant phrasings

### match the band to your URL count instead of maxing everything

## Why it happens

Bright Data's official skills repo (brightdata/skills, concurrency-guide.md) quick decision guide for Web Unlocker scale: under 50 URLs sequential is fine; 50 to 500 URLs use concurrent requests with a semaphore at concurrency 10 to 20; 500 to 10,000 URLs use concurrency 20 to 50 plus progress tracking; 10,000 plus use concurrent plus batch into chunks of 1,000 and save intermediate results. The endpoint is POST https://api.brightdata.com/request with the zone, url, and format in the JSON body, Authorization Bearer header.

## Edge cases

- If your error message differs even slightly, this is probably a different issue; search the exact text.
- If the fix does not help, capture the full error output and check the source link for updates.

## Source

https://github.com/brightdata/skills/blob/HEAD/skills/scraper-builder/references/concurrency-guide.md