Interesting writeup. The serverless approach helped with GTM. (I speculate) raising capital afforded them extra devs who noticed the cache latency.
Unlikely? They could've just as well deployed their single go binary to a vm from day 1 and it would've been smooth sailing for their use case, while they acquire customers.
The cloudflare workers they chose aren't really suited for latency critical, high throughput APIs they were designing.