(Micro)services and separate codebases are orthogonal. You can have multiple separate components (libraries) implemented in different codebases and linked as a

(Micro)services and separate codebases are orthogonal. You can have multiple separate components (libraries) implemented in different codebases and linked as a single executable (which is actually really common). You can have (micro)services deployed from as single huge codebase - just take a look at all so-called monorepos.