chat.langchain.com slow on localhost & vercel

[kientv]

I have tried to deploy chat.langchain.com source code to vercel.
But the message response very slow, much slow than on chat.langchain.com.

For example in this chain:

Why it need 0.25s for a compaire statement:

const hasHistoryCheckFn = RunnableLambda.from(
    (input: RetrievalChainInput) => input.chat_history.length > 0,
  )

[kientv]

Do someone know why?