As you know, NGINX is using Lua-based scripting on their server configuration. And nginScript itself created to enhance the old configuration scheme. Accoring to Igor Sysoev, nginScript can be used for quick fixes, making NGINX configuration more convenient and operations more efficient way.
ngingScript allows developers to filter and manage traffic at runtime
Sysoev says that nginScript can be successfully used against abusive traffic, by simplifying the procedures needed to filter, rate-limit, and deny requests.