Front-end optimization can only do so much when the server takes a second to respond. Time to First Byte (TTFB) depends on the web server, PHP configuration, opcode caching, database queries and caching layers working together.
I configure and tune Linux servers running Nginx or LiteSpeed, PHP-FPM with OPcache, and MySQL/MariaDB — and add page and object caching where appropriate — so your site responds quickly and stays stable during traffic spikes such as festivals, launches or viral posts.