[spion]

If you are using a database, a server and clients, you already have a distributed system.

You'll also likely use multiple databases (caching in e. g. Redis) and a job queue for longer tasks.

You'll also probably already have multiple instances talking to the databases, as well as multiple workers processing jobs.

Pretending that the monolith is a single thing is sneakily misleading. It's already a distributed system

[fendy3002]

Indeed. So with monolith usually we already have 3-4 (or more) somewhat reliable systems, and one non-reliable system which is your monolithic app. Why add other non reliable systems if you don't really need it?

Making a system to be reliable is really really hard and take many resources, which seldom companies pursuit.

[spion]

just because all the code is in one place doesn't mean its one system.