Tips and best practices for WordPress instances in Amazon Lightsail

This guide collects practical tips for keeping a WordPress instance on Amazon Lightsail fast, stable, and secure.

Keep your site secure and up to date

Keep WordPress, themes, and plugins updated

Back up before you make changes

Before editing configuration files or installing plugins, take a snapshot of your instance so you can easily restore your application from the snapshot in case something goes wrong:

For instructions, see Back up Linux/Unix Lightsail instances with snapshots and Configure automatic snapshots.

Monitoring and troubleshooting

How do I know if my instance is running out of memory?

Common symptoms include:

To confirm, connect to your instance over SSH and check current memory use:

free -m

Look at the available column under Mem:. This is how much memory your instance can still use. If available is below 50 MB, your instance is under heavy memory pressure and is at risk of OOM-killing processes.

You can also check whether the kernel has terminated a process for running out of memory (an "OOM kill"):

sudo dmesg | grep -i "out of memory"

If you see entries mentioning mariadbd or mysqld, your database is being terminated under memory pressure, and the steps in Improve memory performance should help.

Does my instance already have automatic memory tuning?

The newer Lightsail WordPress blueprint includes a service that detects the instance's memory size and applies the swap, MariaDB, and Apache/PHP settings described in this guide automatically each time the instance starts, including after you start or reboot it. To check whether your instance has it, connect over SSH and run:

systemctl status lightsail-memory-config

If the service exists, your instance already manages these settings automatically and you do not need to apply them manually. If the command reports that the unit could not be found, follow the steps in Improve memory performance.

Optimize performance

Choose the right bundle for your workload

The most effective way to improve WordPress performance is to run on an instance bundle with enough memory for your workload. WordPress itself is lightweight; however plugins, themes, and the database can consume significant memory.

As your site grows and needs more resources, you can upgrade to a larger bundle by creating a snapshot and launching a new, larger instance from it.

Improve memory performance

If your site displays "Error establishing a database connection" when you (or your visitors) try to load a page, or you see log messages indicating MariaDB was killed due to out of memory (such as Out of memory: Killed process ... (mariadbd) in the system log), your instance is most likely running out of memory. On smaller instances, the Linux kernel may terminate the MariaDB database process (an "OOM kill") when memory is exhausted.

The three steps below reduce memory pressure by adding swap space and bounding how much memory the database and web server are allowed to use. Each step helps on its own, so you can apply only the ones you need, or all three for the greatest effect. Before you start, make sure you have the latest snapshot of your instance. See Back up before you make changes for more details.

To connect to your instance, use the browser-based SSH client in the Lightsail console, or see Connect to your Linux or Unix instance.

Step 1: Add a swap file

A swap file gives the operating system room to offload inactive memory to disk, which helps prevent out-of-memory crashes on instances with less than about 1.5 GB of RAM. We recommend adding swap on nano or micro bundles, and it is usually unnecessary on larger ones.

First, check whether swap is already active:

cat /proc/swaps

If the only line printed is the header (no swap entries listed), no swap is configured:

Filename                Type        Size       Used    Priority

Create a 650 MB swap file:

sudo dd if=/dev/zero of=/mnt/.lightsail.swap bs=1K count=665600 status=progress
sudo chmod 600 /mnt/.lightsail.swap
sudo mkswap /mnt/.lightsail.swap
sudo swapon /mnt/.lightsail.swap

To make the swap file persist across reboots, add it to /etc/fstab:

echo '/mnt/.lightsail.swap none swap sw 0 0' | sudo tee -a /etc/fstab

Confirm swap is now active:

cat /proc/swaps

The swap file now appears in the output:

Filename                Type        Size       Used    Priority
/mnt/.lightsail.swap    file        665596     0       -2

Step 2: Tune the MariaDB database

innodb_buffer_pool_size is the largest single memory consumer in MariaDB. If the default pool size is too large compared to the instance memory, it can contribute to out-of-memory crashes.

Find the recommended innodb_buffer_pool_size for your instance from the recommended configuration table, then create a dedicated configuration file with that value (replace 16M in the example with your value):

sudo tee /etc/mysql/mariadb.conf.d/90-lightsail-memory.cnf > /dev/null <<'EOF'
[mysqld]
innodb_buffer_pool_size = 16M
EOF

To execute the change, run the following command that restarts the database:

sudo systemctl restart mariadb

Step 3: Tune Apache and PHP

Apache is the web server that handles incoming requests to your WordPress site. By default, it allows up to 150 simultaneous worker processes (MaxRequestWorkers). On a small instance, each PHP worker can use tens of megabytes, which can exhaust memory under load. To limit the number of workers to match your instance, and bound how much memory a single PHP request may use, set the Apache mpm_prefork limits (values shown are for a micro instance; check the recommended configuration table for your instance):

sudo tee /etc/apache2/mods-available/mpm_prefork.conf > /dev/null <<'EOF'
<IfModule mpm_prefork_module>
    StartServers            1
    MinSpareServers         1
    MaxSpareServers         3
    MaxRequestWorkers       5
    MaxConnectionsPerChild  5000
</IfModule>
EOF

Set the PHP memory_limit (512 MB is a safe upper bound for all sizes). First detect your PHP version, then write the configuration file:

PHP_VERSION=$(php -r 'echo PHP_MAJOR_VERSION.".".PHP_MINOR_VERSION;')
sudo mkdir -p /etc/php/${PHP_VERSION}/apache2/conf.d
sudo tee /etc/php/${PHP_VERSION}/apache2/conf.d/90-lightsail-memory.ini > /dev/null <<'EOF'
memory_limit = 512M
EOF

Apply both changes by restarting Apache:

sudo systemctl restart apache2

Recommended values by instance memory

Use the values below based on your instance's total RAM. To check your instance's memory, run free -m and look at the total column, or refer to your bundle size in the Lightsail console.

Use caching to reduce load

Caching reduces how often WordPress has to query the database and run PHP, which lowers both CPU and memory usage: