LangChain is the new cool kid on the block. It's a library designed to help you interact with Large Language Models (LLMs). It simplifies many of the routine tasks associated with working with LLMs, such as extracting text from documents or indexing them in a vector database. If you're working with LLMs today, LangChain can save you hours of work. Combing LangChain and battle-tested tools like Elasticsearch in one of the most common LLM applications: semantic search. In this tutorial, I'll walk you through building a semantic search service using Elasticsearch, OpenAI, LangChain, and FastAPI.