Real-time voice AI systems are designed to support natural human conversation by minimizing latency and enhancing responsiveness through concurrent processing architectures. Unlike traditional sequential systems, these voice agents require multiple stages, such as audio capture, speech-to-text (STT), natural language understanding, response generation, and text-to-speech (TTS) synthesis, to operate in parallel. This approach reduces perceived delay and improves the flow of conversation. Streaming STT provides partial transcriptions quickly to enable early processing, while pre-emptive TTS begins generating responses based on predicted user intent. Effective concurrency design involves managing asynchronous tasks, thread pools, and actor models to prevent race conditions and resource contention. Challenges such as audio race conditions, STT flooding, and backpressure during high traffic are addressed through techniques like handshake mechanisms, debounce thresholds, and circuit breakers to maintain system reliability and performance. The focus on concurrency is crucial for developing voice AI systems that feel natural, responsive, and engaging, and companies like Gladia offer tools to optimize these processes for improved voice agent capabilities.