22 August 2026

#LangChain


Key Concepts


S.No Topic Sub-Topics
1 LangChain LangChain architecture, LLMs, ChatModels, Prompts, Messages, Chains, Runnables
2 Models & Providers OpenAI, Anthropic, Google Gemini, Ollama, model configuration, temperature, token limits
3 Prompt Engineering Prompt templates, ChatPromptTemplate, system messages, variables, few-shot prompts, output control, prompt composition
4 Messages & Chat HumanMessage, AIMessage, SystemMessage, message history, message placeholders, multimodal messages, message filtering
5 Output Parsers String output, JSON output, Pydantic parser, structured output, validation, error handling, schema design
6 Runnables Runnable interface, RunnableSequence, RunnableParallel, RunnableLambda, RunnablePassthrough, RunnableBranch, RunnableConfig
7 LCEL Pipe operator, chain composition, parallel execution, branching, streaming, batch execution, reusable chains
8 Chains LLM chains, prompt + model chains, sequential chains, conditional chains, transformation chains, custom chains, chain debugging
9 Tool Calling Tool definition, tool schemas, function calling, model binding, tool invocation, tool results, tool errors
10 Agents Agent architecture, agent loop, tool selection, AgentExecutor, ReAct, custom agents, agent errors
11 Agentic Workflows Planning, reasoning, tool execution, routing, decision making, retries, human-in-the-loop
12 Memory Conversation memory, message history, RunnableWithMessageHistory, persistent memory, session management, memory limits, summarization
13 Document Loaders PDF loader, web loader, text loader, CSV loader, JSON loader, directory loader, custom loaders
14 Document Processing Documents, metadata, cleaning, normalization, splitting strategy, duplicate removal, document pipelines
15 Text Splitters RecursiveCharacterTextSplitter, token splitting, semantic splitting, chunk size, overlap, custom splitting, chunk optimization
16 Embeddings Embedding models, vector representation, similarity, OpenAI embeddings, local embeddings, batch embeddings, embedding evaluation
17 Vector Stores Chroma, FAISS, Pinecone, Milvus, Weaviate, PGVector, vector-store abstraction
18 Retrieval Similarity search, MMR, metadata filtering, top-k, retriever interface, contextual retrieval, custom retrievers
19 RAG Fundamentals RAG architecture, indexing pipeline, retrieval pipeline, prompt construction, context injection, answer generation, citations
20 Advanced RAG Multi-query retrieval, contextual compression, parent-child retrieval, hybrid search, reranking, query transformation, self-query retrieval
21 Retrieval Quality Precision, recall, relevance, chunk evaluation, retrieval evaluation, hallucination detection, RAG benchmarking
22 Structured Data & SQL SQLDatabase, SQL agents, database tools, natural-language queries, query validation, schema awareness, SQL security
23 LangChain + APIs REST APIs, custom tools, external services, authentication, request handling, response parsing, API error handling
24 LangGraph Integration Graph concepts, state, nodes, edges, conditional routing, persistence, human approval, LangChain vs LangGraph
25 Streaming Token streaming, Runnable streaming, agent streaming, custom events, async streaming, UI integration, real-time responses
26 Async & Performance Async invoke, parallel execution, batching, concurrency, caching, token optimization, latency optimization
27 Observability LangSmith, tracing, runs, prompts, tool traces, debugging, evaluation datasets
28 Production RAG Application Architecture, ingestion service, retrieval service, LLM service, API layer, security, deployment
29 Production Agents Agent architecture, tool security, guardrails, retries, timeouts, state persistence, failure recovery
30 Expert Capstone Production RAG, agentic RAG, multi-tool agent, LangGraph workflow, evaluation, monitoring, deployment

Interview question

What is LangChain?
Why was LangChain created?
What are the main components of LangChain?
What problems does LangChain solve?
What are the core abstractions in LangChain?
What is an LLM in LangChain?
What is a Chat Model in LangChain?
What is the difference between an LLM and a Chat Model?
What is a prompt in LangChain?
What is a PromptTemplate?
What is a ChatPromptTemplate?
What is a SystemMessage in LangChain?
What is a HumanMessage in LangChain?
What is an AIMessage in LangChain?
What is message history in LangChain?
What is output parsing in LangChain?
What is a StrOutputParser?
What is structured output in LangChain?
How do you generate JSON output using LangChain?
How do you validate LLM output in LangChain?
What is an Embedding Model?
Why are embeddings used in LangChain?
What is a vector embedding?
What is semantic similarity?
What is a Vector Store?
What vector stores are supported by LangChain?
What is Chroma in LangChain?
What is FAISS?
What is Pinecone?
What is Milvus?
What is Weaviate?
What is the difference between a vector database and a relational database?
How does LangChain perform similarity search?
What is similarity search with score?
What is Maximum Marginal Relevance?
Why is MMR useful in RAG applications?
What is a retriever in LangChain?
What is the difference between a retriever and a vector store?
How do you convert a vector store into a retriever?
What is a MultiQueryRetriever?
What is a Document in LangChain?
What are the main fields of a LangChain Document?
What is document metadata?
Why is metadata important in RAG?
What is a Document Loader?
What document loaders are available in LangChain?
How do you load a PDF using LangChain?
How do you load a text file using LangChain?
How do you load CSV files using LangChain?
How do you load JSON files using LangChain?
How do you load web pages using LangChain?
How do you load documents from a directory?
What is DirectoryLoader?
What is PyPDFLoader?
What is WebBaseLoader?
What is UnstructuredLoader?
What is a RecursiveCharacterTextSplitter?
Why is recursive text splitting preferred?
What is chunk size?
What is chunk overlap?
What is text splitting in LangChain?
Why do documents need to be split into chunks?
How do you choose an appropriate chunk size?
How does chunk overlap affect retrieval?
What happens if the chunk size is too small?
What happens if the chunk size is too large?
What is token-based text splitting?
What is character-based text splitting?
What is recursive splitting?
What is MarkdownHeaderTextSplitter?
What is HTMLHeaderTextSplitter?
How do you split code using LangChain?
How do you preserve metadata during document splitting?
How can you optimize document chunking for RAG?
What is parent-child document retrieval?
What is contextual chunking?
What is semantic chunking?
What is the difference between fixed-size and semantic chunking?
How does chunking affect embedding quality?
How does chunking affect retrieval accuracy?
What is RAG?
How does Retrieval-Augmented Generation work?
What are the main stages of a LangChain RAG pipeline?
What is the difference between indexing and retrieval?
How do you build a basic RAG application using LangChain?
What is a RetrievalQA chain?
What replaced older RetrievalQA patterns in modern LangChain?
What is create_retrieval_chain?
What is create_stuff_documents_chain?
What is the StuffDocumentsChain approach?
What is MapReduce document processing?
What is Refine document processing?
What is the difference between Stuff, MapReduce, and Refine?
How does LangChain handle retrieved documents?
How do you pass retrieved documents to an LLM?
How do you add citations to a RAG response?
How do you prevent hallucinations in RAG?
What are common RAG failure modes?
How do you improve RAG retrieval quality?
How do you evaluate a LangChain RAG application?
What is LCEL?
What does LCEL stand for?
Why was LCEL introduced?
What is a Runnable in LangChain?
What is RunnableSequence?
What is RunnableParallel?
What is RunnablePassthrough?
What is RunnableLambda?
What is RunnableBranch?
What does the pipe operator do in LCEL?
How do you compose multiple Runnable components?
What is the difference between Chain and Runnable?
Why is Runnable preferred in modern LangChain?
How do you invoke a Runnable?
What is the difference between invoke and run?
What is batch execution in LangChain?
What is stream execution in LangChain?
What is astream in LangChain?
How does async execution work in LangChain?
How do you handle parallel execution with LCEL?
What is an Agent in LangChain?
What is an AgentExecutor?
How does a LangChain agent work?
What is tool calling?
What is a Tool in LangChain?
How do you create a custom tool?
What is the @tool decorator?
How does an agent select a tool?
What is tool input schema?
How do you validate tool arguments?
What is the difference between a tool and a function?
What is function calling?
What is the difference between function calling and tool calling?
What is ReAct in LangChain?
How does the ReAct agent work?
What are the advantages of agents over chains?
What are the disadvantages of agents?
When should you use an agent instead of a chain?
How do you restrict an agent from using unauthorized tools?
How do you handle tool execution errors?
What is memory in LangChain?
Why is conversation memory required?
What is conversation history?
What is RunnableWithMessageHistory?
How do you maintain chat history in LangChain?
What is the difference between short-term and long-term memory?
How can conversation history exceed the context window?
How do you summarize conversation history?
How can vector stores be used as long-term memory?
How do you persist conversation history?
What is LangSmith?
Why is LangSmith used with LangChain?
What is tracing in LangSmith?
How do you trace a LangChain application?
What is observability in LLM applications?
How do you debug a LangChain chain?
How do you monitor token usage?
How do you monitor latency in LangChain?
How do you evaluate LLM responses?
What is an evaluation dataset?
What are common RAG evaluation metrics?
What is retrieval relevance?
What is answer correctness?
What is faithfulness in RAG evaluation?
How do you compare two prompts using LangSmith?
How do you integrate OpenAI with LangChain?
How do you integrate Anthropic with LangChain?
How do you integrate Google Gemini with LangChain?
How do you integrate Ollama with LangChain?
How do you use local LLMs with LangChain?
How do you configure API keys in LangChain?
How do you manage secrets securely in a LangChain application?
How do you configure temperature?
What is max_tokens?
How do model parameters affect LangChain applications?
How do you implement streaming responses in LangChain?
How do you stream tokens from an LLM?
How do you handle callbacks in LangChain?
What are callbacks used for?
How do you implement logging in LangChain?
How do you handle exceptions in LangChain?
How do you implement retries?
What is with_retry in LangChain?
How do you implement fallbacks?
What is with_fallbacks in LangChain?
How do you build a conversational RAG system?
How do you combine chat history with RAG?
What is history-aware retrieval?
What is create_history_aware_retriever?
How do you rewrite follow-up questions before retrieval?
How do you handle ambiguous user queries in RAG?
How do you implement metadata filtering in retrieval?
How do you retrieve documents based on user-specific permissions?
How do you implement hybrid search with LangChain?
What is keyword search?
What is BM25 retrieval?
How do you combine BM25 and vector search?
What is ensemble retrieval?
What is contextual compression retrieval?
What is ContextualCompressionRetriever?
What is a reranker?
Why is reranking useful in RAG?
How do you implement reranking in LangChain?
What is ParentDocumentRetriever?
When should you use ParentDocumentRetriever?
How do you secure a LangChain application?
What is prompt injection?
How can LangChain applications defend against prompt injection?
What is indirect prompt injection?
How do you prevent sensitive data leakage?
How do you restrict agent tool permissions?
How do you validate external tool outputs?
How do you implement guardrails around LangChain?
How do you prevent an agent from executing dangerous operations?
How do you implement human approval for agent actions?
How do you optimize LangChain application performance?
How do you reduce LLM token usage?
How do you reduce RAG latency?
How do you cache LLM responses?
What is caching in LangChain?
How do you batch multiple LLM requests?
How do you parallelize independent LangChain operations?
How do you optimize vector search?
How do you optimize embedding generation?
How do you design LangChain for production?
What are common LangChain production challenges?
How do you version prompts in production?
How do you test LangChain chains?
How do you unit test a LangChain application?
How do you mock an LLM during testing?
How do you test retrieval independently?
How do you test agent tool selection?
How do you handle LLM provider outages?
How do you design multi-model fallback architecture?
How do you deploy LangChain applications?
What is the difference between LangChain and LangGraph?
When should LangGraph be used instead of LangChain agents?
How does LangChain integrate with LangGraph?
What is a stateful agent workflow?
What is an AI workflow in LangChain?
What is the difference between deterministic workflows and agents?
How do you build multi-step workflows with LangChain?
How do you implement conditional execution?
How do you implement parallel branches?
How do you combine retrieval, tools, and LLM calls?
What is the difference between LangChain legacy APIs and modern LangChain APIs?
What are deprecated LangChain chains?
Why is LCEL important for modern LangChain development?
How do you migrate legacy chains to Runnable-based pipelines?
How do you migrate old agent implementations to modern agents?
How do LangChain packages separate integrations?
What is langchain-core?
What is langchain-community?
What is the purpose of provider-specific LangChain packages?
How do you keep LangChain dependencies maintainable in production?
Design a production-ready RAG application using LangChain.
Design a PDF question-answering system using LangChain.
Design a multi-document RAG system using LangChain.
Design a chatbot with persistent conversation history.
Design an enterprise document search system using LangChain.
Design a resume screening application using LangChain.
Design an agent that uses database and web-search tools.
Design a customer-support agent using LangChain.
Design a secure enterprise RAG system with document-level access control.
Design a scalable LangChain architecture for millions of documents.

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