You should definitely check some of the threads over the last 5 years on HN around interviewing. My personal rule of thumb is even if I'm 110% qualified for a position, landing a good job as an engineer requires 1-2 months of hard leetcode study. Then, assuming a good personality, no red flags, you get up to a 50-60% chance of passing any given interview.

Its incredibly time consuming and can also be quite stressful and dehumanizing, as you'll be leaving a lot of interview rooms thinking you're an imposter when the process is just awful.