LiveKit, a developer of infrastructure software for real-time AI voice and video applications, has announced the raise of $100 million in funding at a $1 billion valuation.

The round, which comes ten months after LiveKit’s previous fundraise, was led by Index Ventures with participation of existing investors including Altimeter Capital Management, Hanabi Capital and Redpoint Ventures.

LiveKit powers OpenAI’s ChatGPT voice mode. The startup’s other customers include xAI, Salesforce, Tesla, as well as 911 emergency service operators and mental health providers.

The company was founded in 2021 by Russ d’Sa and David Zhao as an open-source software project for building apps that can transmit real-time audio and video without interruptions, in an era when the whole world was meeting on Zoom during the pandemic.

Although LiveKit began as a free developer tool, the business took off after the founders realized big companies wanted a managed cloud version and began providing those services to enterprises amid the voice AI boom.