---
"@context": https://schema.org
"@type": TechArticle
"@id": https://www.twilio.com/docs/api/errors/420027#article
headline: "420027: Knowledge source service unavailable"
url: https://www.twilio.com/docs/api/errors/420027
inLanguage: en
dateModified: 2026-07-29T18:16:50.000Z
author:
  "@type": Organization
  name: Twilio Developer Education Team
publisher:
  "@type": Organization
  name: Twilio
---

# 420027: Knowledge source service unavailable

Log Type: TWILIO

Log Level: ERROR

## Description

The web crawler received a `503 Service Unavailable` response when attempting to access the target URL during knowledge ingestion. The target server is temporarily unable to handle the request.

### Possible causes

* The target site is undergoing maintenance
* Server overload or resource exhaustion
* Temporary service outages or disruptions
* The site is intentionally down for upgrades
* Backend services or databases are unavailable

### Possible solutions

* Verify the target URL loads correctly in a web browser
* Check if the target site has announced maintenance windows or service issues
* If the error is temporary, the crawler will automatically retry on the next scheduled crawl
* For persistent unavailability, verify the URL is correct and the site is operational
* Consider scheduling crawls during times when the site is less likely to be under maintenance
* Review the knowledge source error details in the Twilio Console