I am awesome. As an added bonus, I'm always right. And if you don't believe me, i'll show you the metrics on how your bad code affected the production systems.

Yes, being in the same process is very helpful! That is, until you have to scale your website. Uh oh, you have maxed out your server. Okay, you buy a bigger server. Time passes. Congratulations, your site is very successful and you max it out! Too bad your now-popular app is riddled with assumptions that come from all requests being inside the same process.

Learn from the big guns of websites -- scale horizontally. Frontend proxies load balancing across multiple backend servers. Redundancy and scalability. Definitely don't assume all of a user's requests will come to the same server. For goodness sake, though, don't start out fundamentally limited in your potential scale.