Implement caching methods to lessen the server's load. Utilize both server-side caching (like Opcode caching) and client-side caching (using tools like Varnish or CDN services).
Distribute static content through a CDN. This reduces the load on your server by serving static files from servers geographically closer to your users.
Consider using load balancing to spread incoming traffic among multiple servers. This helps prevent a single server from becoming a bottleneck.
Optimize your database queries to reduce the time it takes to fetch data. Use indexes, optimize poorly performing queries, and consider database caching.
Implement proper error handling to prevent crashes due to unexpected traffic spikes. Users should receive meaningful error messages instead of a server crash.