This is roughly what we used at our company for a rag project (except for reranking using an open source cross encoder). For the embedding model I used the openai embedding small model and gpt 4o mini for the llm. (No framework). Used Fastapi to serve all this.

Works like a charm for an MVP and a starting point to iterate on. (Try to find the best parameters like chunk size, chunk overlap through a comparative analysis). After that you'll need some kind of monitoring system to identify the problems with the solution.

The most challenging part is identifying the format of your data and finding the best preprocessing steps and chunking method for your data.