Besides searching on Glassdoor or Indeed, how can someone find a list of companies that are doing this type of work? Are they limited to the east coast? I'm no

Besides searching on Glassdoor or Indeed, how can someone find a list of companies that are doing this type of work? Are they limited to the east coast? I'm not very familiar with the HFT industry, but the skills that they require (C++, computer architecture, OS, networking, & performance) are ones that I'm interested in and would love to deepen my experience with. Are there companies on the west coast (more specifically southern California) where one could develop this experience?