TTFB is the abbreviation for Time to First Byte.

The time to first byte (TTFB) indicates how long it takes the user to receive the first byte of website data from your host / server. When a user makes an HTTP request (loads your webpage), the TTFB is essentially the waiting time before data is received.

The TTFB should be around 200 ms (according to Google). For websites with poor hosting that have not yet been optimized, the TTFB can easily be 2 seconds or longer.

The TTFB delay on your Divi site is usually caused by:

The amount of dynamic content that must be received. This can be reduced through caching, database optimization and a CDN.
The amount of traffic your server is experiencing at this point in time. Traditional (or shared) hosting providers make it difficult to shut down this TTFB because you are sharing resources with others on the same server. Traffic spikes slow down your server’s processing speed.
Your web server configuration. A good WordPress hosting provider can help with the TTFB of your site by providing solid backend infrastructure and tweaking your web server configuration (things that you virtually can’t control).
In short, if you want a quick boost to TTFB, get better hosting and follow the rest of the steps below.