Resource Monitoring: Use htop to check for CPU and RAM usage peaks. Disk I/O: Tools like iostat -xz 1 or iotop show disk load. Network Traffic: Monitor real-time traffic with iftop. Application Logs: Check /var/log (Apache, Nginx, PHP-FPM) for errors. Database Optimization: Enable MySQL/MariaDB slow query log (/etc/mysql/my.cnf) and analyze slow queries. Caching: Implement Redis or Memcached to cache data and reduce database load.