> At that point you can well afford to hire people who are deep experts at sharding etc.

Can you, though? OpenAI is haemorrhaging money like it is going out of style and, according to the news cycle over the last couple of days, will likely to be bankrupt by 2027.

And typically the bigger the company gets, the harder it is to migrate to a new data model.

You suddenly have literally thousands of internal users of a datastore, and "We want to shard by userId, nobody please don't do joins on user Id anymore" becomes an impossible ask.