The Libera Chat network—libera.chat—has chat rooms dedicated to Wikipedia 24 hours a day, in which Wikipedians can engage in real-time discussions with each other. Many Wikipedians have IRC chatting open in one window and hop back and forth between it and other windows in which they are working on Wikipedia.
You can set your computer to make a sound or your browser tab to flash when you have IRC open while somebody is replying to you. Users with a "+" sign next to their nickname are volunteer IRC helpers.