- Everybody in their right mind agreed that, for what they were achieving, Twitter was completely over-staffed. Like most of the big tech co in this period. And like most of those co, they went through a leaning program with mass layoffs.
- If the service is running fine with only 10% of the staff, it doesn't necessarily means that the 90% that got fired were useless. I can get a 6yo to heat their food using a microwave. Does it mean that the kid is a genius, or that the people who made the microwave did it in a way that allows a kid to operate it, even though it's a complex system at its core?
- Comparing Twitter to an international eCom website is disingenuous. If "design Twitter" is a common system design interview question, it's not because the website is popular, it's because the basics are quite simple. Whereas, behind an eCom website, there's dozens of parts going on at any time, with hundreds of interoperability issues. You're not mainly relying on your main DB for your data, most of it is coming from external systems.