LangChain & LlamaIndex: Orchestration Frameworks

MEDIUM8 min readby AdminJune 19, 2026History
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Compare LangChain and LlamaIndex orchestration libraries with clear Python code examples.

#ai-engineering#langchain#llamaindex#orchestration#python

Choosing Orchestration Frameworks

LLM orchestration frameworks simplify building AI pipelines:

• LangChain: Highly modular and action-oriented. Best for building conversational chat agents, complex pipelines, and multi-step tool integrations. • LlamaIndex: Data-oriented. Built specifically for ingestion, advanced indexing, and structured retrieval, making it the preferred choice for complex RAG architectures.

LangChain Prompt Template & LLM Chain (Python)

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from langchain_core.prompts import ChatPromptTemplate
from langchain_openai import ChatOpenAI

# Instantiate LLM
llm = ChatOpenAI(model="gpt-4o", temperature=0.2)

# Define template
prompt = ChatPromptTemplate.from_messages([
    ("system", "You are a tech interview coach. Answer concisely."),
    ("user", "Explain the concept of {concept}")
])

# Combine using LangChain Expression Language (LCEL)
chain = prompt | llm

response = chain.invoke({"concept": "Vector Embeddings"})
print(response.content)

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