> Then there came async frameworks a la Node, Twisted et al. and changed everything. Again in my opinion, async code is harder to reason about versus synchronou

> Then there came async frameworks a la Node, Twisted et al. and changed everything. Again in my opinion, async code is harder to reason about versus synchronous code. One change here which has also made this less important is the trend toward serverless/microservice architecture. In a world where you were running your MVP on a single VPS instance somewhere, and you were running a monolithic webserver which handled everything from request parsing to business logic, then moving from one-thread-per-request to a runloop implementation represented a potentially huge win in terms of performance. But nowadays we largely work with more atomized bits of logic: business logic is implemented in terms of small, self-contained operations, and the problems of scale are delegated to some other system or orchestration framework. In that world it matters much less if your database access is blocking a thread or not, because throughput issues can be solved at a different level.