Varnish Cache is a popular – and powerful – open source HTTP engine/reverse HTTP proxy used by more than 3.4 million websites.

Varnish Cache is an open-source reverse HTTP proxy that is used by millions of websites worldwide for web acceleration and content caching. When deployed on Digital Ocean, it can cache HTTP content to speed up delivery significantly (300 - 1000%!) and reduce backend server load by up to 99%. It does this by caching and storing a copy of the web content the first time a user visits, and then delivering it directly from the cache for future requests. This means your web service can stay fast and online even during busy periods, providing an excellent web experience to your visitors at all times. Varnish Cache 6.0.7 is the latest LTS release.

More info:

https://www.varnish-software.com/resources/