There are lots of requests from the visitors especially from David T. upon how to optimize Apache, php and MySQL/Mariadb server which are installed on VPS server with 1gb of RAM, Such 1 gb ram vps is enough powerful for single application and optimizations are necessary in order to Avoid OOM (out of memory) and take juice from it.

Optimization of Apache :

Optimize Apache which is installed on 1gb VPS, it recommended to use Apache MPM worker as prefork :-

Centos/RHEL:

Under Centos Open this file in editor:

nano /etc/httpd/httpd.conf

And add this configs at the end of httpd.conf :

KeepAlive Off
<IfModule prefork.c>
   StartServers        6
   MinSpareServers     5
   MaxSpareServers     15
   ServerLimit         256
   MaxClients          256
   MaxRequestsPerChild 3000
</IfModule>

Then restart Apache server :

service httpd restart

Ubuntu :

Under Ubuntu Open this file in editor:

nano /etc/apache2/apache2.conf

Find and add/change this configs under apache2.conf file :

<IfModule mpm_prefork_module>
 StartServers        3
 MinSpareServers     5
 MaxSpareServers     15
 ServerLimit         256
 MaxClients          256
 MaxRequestsPerChild 3000
</IfModule>

Then restart Apache server :

service apache2 restart

Optimization of MYSQL :

To optimize MySQL/Mariadb which is installed on 1gb VPS you need to add  this configs in  my.cnf under [mysqld] :

[mysqld]
symbolic-links=0
skip-external-locking
key_buffer_size = 32K
max_allowed_packet = 4M
table_open_cache = 8
sort_buffer_size = 128K
read_buffer_size = 512K
read_rnd_buffer_size = 512K
net_buffer_length = 4K
thread_stack = 480K
innodb_file_per_table
max_connections=100
max_user_connections=50
wait_timeout=50
interactive_timeout=50
long_query_time=5

On Centos/RHEL based system you can add it in :

/etc/my.cnf

On Ubuntu/Debian based system you can add it in :

/etc/mysql/my.cnf 

• Also consider adding SWAP to your VPS which will drastically stabalizes the 1 gb VPS
  
• To optimize PHP just installed php-opcache and memcached (memcached need to be supported by script)
• Configure PHP memory limit not more than 128 mb.
• Use cache system which is provided by your script or for WordPress use WP super cache.