Servlets and Jakarta EE
1997–today Sun, Oracle, Eclipse Foundation. Still developed
Java’s server API since 1997, now Jakarta EE at the Eclipse Foundation. Spring Boot, Struts, Vaadin, and Javalin run in servlet containers like Tomcat and Jetty, and Helidon implements its APIs.
Tornado and asyncio
2009–today FriendFeed, Python community. Still developed
Python event-loop servers older than ASGI. Tornado came out of FriendFeed in 2009, aiohttp and Sanic run on asyncio, and Streamlit serves its apps with Tornado.
Rack
2007–today Christian Neukirchen. Still developed
Ruby’s interface between web servers and apps, inspired by Python’s WSGI. Rails, Sinatra, and Hanami are all Rack apps.
ASP.NET Core
2016–today Microsoft. Still developed
Microsoft’s open-source, cross-platform rewrite of ASP.NET with the Kestrel web server. Blazor runs on it.
net/http
2012–today Go team, Google. Still developed
Go’s standard HTTP server is good enough that most Go frameworks are routers and middleware on top of it: Gin, Echo, Chi, Beego.
fasthttp
2015–today Aliaksandr Valialkin. Still developed
A Go HTTP server that gives up net/http compatibility for fewer allocations. Fiber puts an Express-style API on it.
Phoenix and Plug
2014–today Chris McCord, José Valim. Still developed
Elixir’s web framework on Plug and the BEAM virtual machine, built to hold many connections open at once. LiveView grew out of its Channels.
SwiftNIO
2018–today Apple. Still developed
Apple’s event-driven networking library for server-side Swift, modeled on Netty. Vapor runs on it.