Voice AIGemini TTS / OpenAI4-month engagement
Real-Time Voice Assistant with Gemini TTS, OpenAI Reasoning and Optimized Token Management
A client needed a production voice assistant that could hold multi-turn technical conversations, respond in natural speech under 1.5 seconds, and operate at scale without runaway API costs.
Problem
Naive implementation passed the full conversation history to GPT-4o on every turn, causing exponential token growth, high latency, and monthly API costs that made the product economically unviable. TTS responses had 3–4 second delays.
Solution
Built a hybrid voice pipeline: OpenAI Whisper for STT, GPT-4o for reasoning with a custom memory layer, and Google Gemini 2.0 Flash TTS for low-latency speech synthesis. Implemented a sliding window memory system with semantic summarization of older turns.
Technology
OpenAI Whisper (STT), GPT-4o (reasoning), GPT-4o-mini (summarization), Google Gemini 2.0 Flash (TTS), LangChain memory with custom summarizer, WebSocket streaming, Redis session store
1.1s
End-to-end voice response time
85%
Reduction in token usage vs. naive
Unlimited
Conversation turns with stable context
4×
Lower monthly API cost
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