# Apache: [mpm_event:error] AH00484: server reached MaxRequestWorkers setting, consider raising the MaxRequestWorkers setting

**Code:** `AH00161: server reached MaxRequestWorkers setting` · **Category:** Nginx / Apache · **Seen on:** Apache, Linux

Apache used all its worker slots, so new requests queue or time out.

## Meaning

Raise `MaxRequestWorkers` (and `ServerLimit`/`ThreadsPerChild` for event/worker MPM) to fit available RAM (`workers ≈ free RAM / avg process size`). Also fix slow requests holding workers, enable KeepAlive tuning (`KeepAliveTimeout 2-5`), and consider PHP-FPM + event MPM instead of prefork+mod_php.

## Common causes

- Traffic spike or slow backend holding workers
- Default limit (150/256) too low
- Long KeepAlive timeouts
- Prefork MPM with mod_php (memory heavy)
- Slow client attacks

## Quick fix

1. Tune `MaxRequestWorkers` to your RAM
2. Lower `KeepAliveTimeout`, enable `mod_reqtimeout`
3. Switch to event MPM + PHP-FPM

## Detailed fix by platform

### Linux

1. `apachectl -V | grep -i mpm; ps -ylC apache2 --sort:rss | awk '{sum+=$8} END {print sum/NR/1024 " MB avg"}'`

## How to diagnose

1. **Limit** — MaxRequestWorkers?
2. **RAM** — Per-process memory?
3. **Slow** — Long requests?

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Source: [WhatIsMyError](https://whatismyerror.com/errors/nginx-apache/apache-maxrequestworkers-reached)