Are monolithic applications single tiered applications or is it at just code level i.e. UI, Business logic and data access layer in same one big repository? If it is single tiered then does it mean everything is hosted on single server including the database
Is it just code level distinction?
Monolithic applications should be compared to microservices applications distinction being the difference in approach to deployable units (i.e. in monolithic applications the whole app is usually has a single deployable unit which contains everything when in microservices approach you will have multiple deployable ideally independent/loosely coupled units).
Tiered architecture should be compared to things like clean architecture, feature/vertical slices architecture etc. and is more about decomposition of application/deployable unit into subsystems/modules (like client level, application logic level, data access layer). So both monolithic app can be n-tiered or can be not.
does it mean everything is hosted on single server including the database
No it does not.
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