Hacker fits 537,000 ad-blocking domains into a $5 ESP32 dongle using just 50KB RAM

A developer has engineered firmware for a $5 ESP32 microcontroller dongle capable of blocking 537,000 advertising domains. The firmware uses only around 50KB of RAM and can answer blocked DNS lookups in just 10 milliseconds. The project is a remarkable demonstration of low-level software optimisation on severely constrained hardware.