For the retrieval stage, we have developed a highly efficient, CPU-only-friendly text embedding model:

https://huggingface.co/MongoDB/mdbr-leaf-ir

It ranks #1 on a bunch of leaderboards for models of its size. It can be used interchangeably with the model it has been distilled from (https://huggingface.co/Snowflake/snowflake-arctic-embed-m-v1...).

You can see an example comparing semantic (i.e., embeddings-based) search vs bm25 vs hybrid here: http://search-sensei.s3-website-us-east-1.amazonaws.com (warning! It will download ~50MB of data for the model weights and onnx runtime on first load, but should otherwise run smoothly even on a phone)

This mini app illustrates the advantage of semantic vs bm25 search. For instance, embedding models "know" that j lo refers to jennifer lopez.

We have also published the recipe to train this type of models if you were interested in doing so; we show that it can be done on relatively modest hardware and training data is very easy to obtain: https://arxiv.org/abs/2509.12539

For vector generation I started using Meta-LLama-3-8B in april 2024 with Python and Transformers for each text chunk on an RTX-A6000. Wow that thing was fast but noisy and also burns 500W. So a year ago I switched to an M1 Ultra and only had to replace Transformers with Apple's MLX python library. Approximately the same speed but less heat and noise. The Llama model has 4k dimensions so at fp16 thats 8 kilobyte per chunk, which I store in a BLOB column in SQLite via numpy.save(). Between running on the RTX and M1 there is a very small difference in vector output but not enough for me to change retrieval results, regenerate the vectors or change to another LLM.

For retrieval I load all the vectors from the SQlite database into a numpy.array and hand it to FAISS. Faiss-gpu was impressively fast on the RTX6000 and faiss-cpu is slower on the M1 Ultra but still fast enough for my purposes (I'm firing a few queries per day, not per minute). For 5 million chunks memory usage is around 40 GB which both fit into the A6000 and easily fits into the 128GB of the M1 Ultra. It works, I'm happy.

Most of my complex documents are, luckily, Markdown files.

I can recommend https://github.com/tobi/qmd/ . It’s a simple CLI tool for searching in these kinds of files. My previous workflow was based on fzf, but this tool gives better results and enables even more fuzzy queries. I don’t use it for code, though.

Don't use a vector database for code, embeddings are slow and bad for code. Code likes bm25+trigram, that gets better results while keeping search responses snappy.

I'm lucky enough to have 95% of my docs in small markdown markdown files so I'm just... not (+). I'm using SQLite FTS5 (full text search) to build a normal search index and using that. Well, I already had the index so I just wired it up to my mastra agents. Each file has a short description field, so if a keyword search surfaces the doc they check the description and if it matches, load the whole doc.

This took about one hour to set up and works very well.

(+) At least, I don't think this counts as RAG. I'm honestly a bit hazy on the definition. But there's no vectordb anyway.

We started with PGVector just because we already knew Postgres and it was easy to hand over to the operations people.

After some time we noticed a semi-structured field in the prompt had a 100% match with the content needed to process the prompt.

Turns out operators started puting tags both in the input and the documents that needed to match on every use case (not much, about 50 docs).

Now we look for the field first and put the corresponding file in the prompt, then we look for matches in the database using the embedding.

85% of the time we don't need the vectordb.

SQLite works shockingly well. The agents know how to write good queries, know how to chain queries, and can generally manipulate the DB however they need. At nori (https://usenori.ai/watchtower) we use SQLite + vec0 + fts5 for semantic and word search

Kiln wraps up all the parts in on app. Just drag and drop in files. You can easily compare different configs on your dataset: extraction methods, embedding model, search method (BM25, hybrid, vector), etc.

It uses LanceDB and has dozens of different extraction/embedding models to choose from. It even has evals for checking retrieval accuracy, including automatically generating the eval dataset.

You can use its UI, or call the RAG via MCP.

https://github.com/kiln-ai/kiln

https://docs.kiln.tech/docs/documents-and-search-rag

I am using LangChain with a SQLite database - it works pretty well on a 16G GPU, but I started running it on a crappy NUC, which also worked with lesser results.

The real lightbulb moment is when you realise the ONLY thing a RAG passes to the LLM is a short string of search results with small chunks of text. This changes it from 'magic' to 'ahh, ok - I need better search results'. With small models you cannot pass a lot of search results ( TOP_K=5 is probably the limit ), otherwise the small models 'forget context'.

It is fun trying to get decent results - and it is a rabbithole, next step I am going into is pre-summarising files and folders.

I open sourced the code I was using - https://github.com/acutesoftware/lifepim-ai-core