The biggest backend things: models can run on CPU architecture, you still need highly performant CPU, but in cloud there is a way to significantly discount that by relying on spot instances (this doesn't mean GPU isnt viable, we just found a real cost lever here that CPU has supported... but things may change and we know how to test that). Further, distributed and parallel (network) processing are important, especially in retrieval-augmented architectures... thus we've booted python long ago, and the lower level apis aren't simply serializing standard json-- think protobuffer land (tensorflow serving offers inspiration). BTW we never needed any "vector DB" ... the integration of real data is complex, embeddings get created through platforms like Airflow, metadata in a document store, and made available for fast retrieval on low-gravity disk (e.g. built on top of something like rocks db... then something like ANN is easy on tools like FAISS).
The biggest UX thing: integration into real-life workflows has to be worked on in a design-centered way, very carefully. Responsible AI means not blindly throwing these type of things into critical workflows. This guides what I assume to be a bit of a complicated frontend effort for most (was for us esp as we integrate into real existing applications... we started prototyping with a chrome extension).
EDIT: btw oss has definitely made some of these things easier (esp for greenfield & simple product architecture), but I'm skeptical of the new popular kids on the block that are vc-funded & building abstractions you'll likely need to break through across software, data, and inference serving for anything in scaled+integrated commercial enterprise.
EDIT2: Monitoring, metrics, and analytics architecture were big efforts as well. Ask yourself how do you measure "value added by AI"