Tell about your experience implementing and managing database replication systems.

In PHP projects, I used database replication to improve fault tolerance and scalability. I typically employed master-slave replication, where the primary database (master) handled write operations, and slaves handled read operations. This allowed offloading the main server and speeding up data reading.

To manage replication, I used the built-in capabilities of the DBMS, such as MySQL with binlog configuration and slave servers. In PHP code, I implemented logic to select the connection — connecting to the slave for read operations and to the master for write operations.

Example of connecting to different servers in PHP:

// Connecting to the master
$master = new PDO('mysql:host=master_host;dbname=testdb', 'user', 'pass');
// Connecting to the slave
$slave = new PDO('mysql:host=slave_host;dbname=testdb', 'user', 'pass');

// For reading
$stmt = $slave->query('SELECT * FROM users');
// For writing
$master->exec("INSERT INTO users (name) VALUES ('John')");

I also monitored replication lag and set up monitoring to avoid reading outdated data.