[diatone]

No concurrency? No events. No more than a single team running a single service (even a monolith)? No events. Not dealing with asynchronous 3rd party APIs (eg: webhooks)? No events. Not dealing with arbitrarily many hosts/processes/tasks/objects communicating with each other, potentially asynchronously? No events. Not streaming? No events.

[hussainbilal]

Basically this. Theoretically, event-driven architecture within a single machine is just re-inventing pi-calculus (i.e. sending values on channels)

So I would imagine anything single-threaded would not require it.

Though admittedly, the only modern application or program that I can think of that would be single-threaded is a CLI command