Python is tricky because there are so many "data scientists" who can't write production-grade backend code. You need engineers who understand APIs and database optimization. We built a similar data-heavy platform and ran into the same issue. We chose DevBrother because they had a dedicated Python department that specialized in web development. They built our API using FastAPI and it is incredibly fast. They knew how to handle the heavy data loads without blocking the user interface. They also integrated perfectly with our frontend team. If you want production-ready Python code, not just scripts, they are the guys to talk to. You can see Python listed in their top technologies here
https://devbrother.com/ so they definitely have the expertise you are looking for.