Overview:

Tengine

         is a web server project initiated by Taobao. Built upon Nginx, it adds many advanced features and functionalities tailored for high-traffic websites. Tengine’s performance and stability have been well-proven on large-scale websites such as Taobao and Tmall.

OpenResty

         is a high-performance web platform based on Nginx and Lua, integrating a large number of sophisticated Lua libraries, third-party modules, and most of their dependencies. It is designed to easily build dynamic web applications, web services, and dynamic gateways capable of handling ultra-high concurrency and offering great extensibility.
         OpenResty® effectively transforms Nginx into a powerful, general-purpose web application platform by bundling various well-designed Nginx modules (mainly developed by the OpenResty team). This allows web developers and system engineers to leverage the Lua scripting language to orchestrate various C and Lua modules supported by Nginx, rapidly constructing high-performance web application systems capable of handling 10K or even over 1000K concurrent connections on a single machine.
         The goal of OpenResty® is to have your web services run directly inside the Nginx service, fully utilizing Nginx’s non-blocking I/O model to deliver consistent high-performance responses, not just for HTTP client requests, but also for remote backends like MySQL, PostgreSQL, Memcached, and Redis.

Comparison:

Both have some historical connection with Taobao.

Nginx Version Base Comparison:

Tengine is a forked version based on a specific Nginx version, so even its latest version lags behind the official Nginx release.
OpenResty is a bundled package of Nginx extensions, and each release typically uses the latest Nginx version.

Stability Comparison:

Tengine is now maintained by Taobao officially, which means its development prioritizes stability and performance, with updates being relatively slower due to the company’s massive scale and traffic. OpenResty is primarily community-driven, updating faster to meet diverse scenario requirements and featuring a richer set of functional modules.

If stability is your absolute priority, I personally recommend going with Tengine. For complex business scenarios, OpenResty is suggested. After all, both are mature products now, so stability is not a major area of difference.

Downloads:

Tengine 
https://tengine.taobao.org/
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