Coming from the Erlang world (very similar to Go as described in the blog post) they're not used for raw speed (in the sense of utilizing more cores). The Erlang VM (or the Go runtime) uses them internally in that way, but for the programmer the benefit is somewhat different.
Processes or co-routines are often used more as concurrent objects. That is, they're used to separate data and concerns into separate, isolated memory areas. However, they're also sequential programs in their own right, so the system becomes much easier to reason about. If you have a few OS thread per core, you are responsible for distributing work among those threads, whereas if you have many co-routines per "job" you can let the runtime decide and schedule intelligently.
A concrete example is a web server. Implemented in Erlang or Go you would typically spawn a co-routine for each incoming connection. There you would get isolation and a simple implementation (parsing the request, performing the task, returning response and exiting). A crash or bug handling a specific request would not affect the other clients.
Other great use cases are messaging and communication apps (examples like Rabbit Q or Discord come to mind), concurrent databases, etc.
Processes or co-routines are often used more as concurrent objects. That is, they're used to separate data and concerns into separate, isolated memory areas. However, they're also sequential programs in their own right, so the system becomes much easier to reason about. If you have a few OS thread per core, you are responsible for distributing work among those threads, whereas if you have many co-routines per "job" you can let the runtime decide and schedule intelligently.
A concrete example is a web server. Implemented in Erlang or Go you would typically spawn a co-routine for each incoming connection. There you would get isolation and a simple implementation (parsing the request, performing the task, returning response and exiting). A crash or bug handling a specific request would not affect the other clients.
Other great use cases are messaging and communication apps (examples like Rabbit Q or Discord come to mind), concurrent databases, etc.