Ask HN: Hardcore CS jobs in LA?

Hi HN. I'm a software engineer, currently living in Los Angeles. For the past 6 years I have worked in various backend systems for big companies. All fairly high-level business logic stuff though (C++ or Java distributed system type stuff).

I would like to get more into hardcore things, for example systems programming in C, or compilers, or RDBMS.

What are some good companies situated in LA doing this kind of thing?