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Next.js + LLMs: The Guide to Streaming Structured Responses

Sai Teja Yalla

In the rapidly evolving landscape of AI-powered applications, delivering a seamless user experience isn't just about what you build—it's about how you deliver it. Today, I’ll share how we implemented LLM response streaming in Next.js, a challenge that reshaped the way our users engage with AI-driven responses. 


Picture this: A user sends a message to your AI chatbot. Instead of staring at a loading spinner for a long time, they can see the response displays word by word, making the conversation feel more engaging and dynamic. 

 

The Challenge 

While our backend services using LLM’s generate accurate responses, users often grew impatient waiting for complete answers. The real technical challenge wasn't just about streaming text, it was about maintaining structured JSON data to support charts and tables generation, all while ensuring the interface stayed responsive and engaging. 


Partial JSON Parsing 

We found partial-json, a library that solved our JSON streaming puzzle. This allowed us to handle incomplete JSON structures gracefully, turning a potential technical nightmare into a smooth user experience.  




The Solution 

Let me share the core implementation of our streaming functionality: 

 

1. Seamlessly Decode Incoming Streams 


The decoding process relies on several key mechanisms: 

  • TextDecoder converts raw binary data into readable text. 

  • Each chunk is processed as it arrives, ensuring smooth data flow. 

  • The buffer accumulates decoded text to handle partial messages. 


If we don't use UTF-8 encoding, streaming chunk by chunk can lead to issues. Without proper encoding, the response might be displayed all at once instead of gradually, disrupting the intended streaming experience. 


2. Managing Partial JSON Data  


The partial JSON handling is crucial because: 

  • Traditional JSON.parse() would fail on incomplete structures 

  • The parse() function (from partial-json) can handle incomplete JSON 


3. Memory Efficiency  


Memory efficiency is achieved through: 

  • Processing one chunk at a time 

  • Not storing the entire response in memory 

  • Clearing the buffer after successful parsing 

  • Using streaming instead of buffering the whole response 


4. Real-time Feedback  


The real-time feedback system: 

  • Immediately processes each chunk as it arrives 

  • Notifies the UI layer through the onChunk callback 

  • Includes a completion flag (isDone) 

  • Allows for progressive UI updates 


Putting It All Together 

Here's how this work together in a typical flow: 

  1. Stream starts:  

  2. Reader is initialized 

  3. Decoder is prepared 

  4. Buffer is emptied 

  5. For each chunk:  

  6. Data is read from the stream 

  7. Chunk is decoded to text 

  8. Added to buffer 

  9. Attempted parsing 

  10. UI is updated if parsing succeeds 

  11. Stream ends:  

  12. Final chunk is processed 

  13. Buffer is cleared 

  14. Completion is signaled 

  15. Resources are cleaned up 


Ready to Implement? 

Here are three key tips from our experience: 

  1. Always implement timeout mechanisms—streams shouldn't hang indefinitely 

  2. Build robust error handling—network issues are inevitable 

  3. Monitor your buffer management—memory usage can creep up with large responses 


Remember, the goal isn't just to stream data—it's to create an experience that makes AI feel more natural and accessible to your users. 


Would you like to share your experiences with LLM streaming? Have you faced similar challenges? Let's continue this conversation in the comments below. 

 

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