I’ve seen plenty of serious backends that use multiple threads and are horizontally scaled. I don’t think this is a particularly compelling argument for the la

I’ve seen plenty of serious backends that use multiple threads and are horizontally scaled. I don’t think this is a particularly compelling argument for the lack of multi-threading. The worker thread pattern is fairly useful and there is no reason a well architected application couldn’t use both horizontal and vertical scaling. Independent scaling is only really useful if there is a large variation in the amount of work done by the workers per query. If it’s well bounded, then it might be easier to just horizontally scale the entire backend. There are also other use cases for threads that don’t fit into the worker pattern. For example, background tasks that happen outside the serving path.