How to Fix a 503 Service Unavailable Error

A 503 Service Unavailable response means the server cannot handle the request right now. The condition may be temporary.

Common causes

• Planned maintenance.
• Traffic spikes or exhausted server resources.
• An application process or dependent service is unavailable.
• Rate limits, deployment restarts, or hosting-platform limits.

How to investigate

1. Check the hosting provider's incident and resource dashboards.
2. Review CPU, memory, worker, connection, and request-limit metrics.
3. Check whether a deployment or maintenance task is still running.
4. Inspect application logs and dependent services such as databases.
5. Scale resources or adjust capacity only when metrics show that is needed.

For planned maintenance, return a clear message and, where appropriate, a Retry-After header. Avoid using 503 for a page that has permanently moved or been removed.