ESP8266 has 64KB DRAM, 96KB SRAM, 32-bit RISC CPU running at 80Mhz and it has to handle also a wireless traffic. Despite this it’s still able to dispatch more than 50 reqs/s on Hello World. And serious optimization hasn’t started yet.
Ref blog : http://www.ureq.solusipse.net/
Ref git :https://github.com/solusipse/ureq