Firecracker looks very promising from a server-side technology stand-point but the support for AMD, RISC-V platforms couldn't be stressed more enough.
Amazon better find a way of supporting AMD processors since Intel's CPU bugs are being brought into the sunlight and exploited in all directions by security researchers which have cataclysmic implications for users and server providers these days. This is demonstrated by a ridiculous Intel vulnerability which rendered Apple's FileVault encryption facilities completely useless which is absolutely unacceptable to Apple. There are many other CPU vulnerabilities waiting to be found and it could be the next Meltdown-like candidate.
The sooner the move to AMD or RISC-V open technologies, the better for developers and users.