Raspberry Pi 3 fast boot in less than 2 seconds! A team has successfully optimized the Raspberry Pi's boot process, reducing it to an impressive 1.0 second. The optimization involves tweaking the kernel and file system to improve read-speed, with options like Hibernate and SquashFS. Additionally, removing unnecessary partitions and optimizing Qt applications can also contribute to faster boot times.

Source: https://www.furkantokac.com/rpi3-fast-boot-less-than-2-seconds/