LlamaIndex and MongoDB together facilitate the use of Large Language Models (LLMs) like ChatGPT to access and query private knowledge sources, overcoming limitations of traditional LLMs that are only trained on publicly available data. LlamaIndex provides a flexible interface to connect LLMs with external data, offering data connectors to various sources and formats, and structures this information to fit within the prompt window limitations of any LLM. MongoDB, as the datastore, supports the storage of ingested documents and indices, facilitating the handling of large datasets and continuous data updates. Through tools like LlamaIndex, users can construct indices from data nodes, enabling secure and efficient querying of private data, such as the GPT-4 Technical Report, which was not part of ChatGPT's original training data. This integration allows for real-time, context-based learning without the need to fine-tune the LLM model constantly, enhancing the practicality and applicability of LLMs in dynamic and private data environments.