How do you spend 80% of a 1.5 million (lets say 800,000 post-tax) salary each year? That'd be an incredibly lavish lifestyle. If you cut your spending down to a cool $200,000/year then you could retire in 5 years and have $150,000/year for the rest of your life.

Let's run a different scenario: your post-tax income is $200k and you save half of that. In 11 years, you can retire and get $100k per year at a 4% withdrawal rate.

People in either of these scenarios are obviously privileged, but the latter isn't unrealistic for a single FAANG dev.

engaging-data.com has cool fire calculators. Highly recommend checking them out