Tech giants publish how they solved real scale problems. Read the Netflix Tech Blog, Uber Engineering Blog, and Meta Engineering articles.
Most importantly, remember that no single book — free or paid — will guarantee you a job. The best preparation uses multiple resources: books, videos, hands-on practice, and real mock interviews. "Hacking The System Design Interview" can be a valuable part of that mix if used correctly. But it's not the only tool you need. Hacking The System Design Interview Stanley Chiang Pdf Free