Redis is an in-memory data store. It is extremely fast and scalable. You can use Redis to store strings, lists, sets of data, and more. Thousands of companies use Redis and it is free and open source. In general, Redis is most often used as an in-memory database or cache.
For our use case, we will use Redis to act as the data store for our Express sessions. Redis is supported on Linux and Mac. It is not officially supported on Windows. You can get unofficial support by using a Docker image on Windows, but that is beyond the scope of this book. However, you can usually get free Linux VM's on cloud providers for a trial period. So if you're on Windows, you could try one of those services.
Redis.conf has a setting called bind which sets the local IP address, the Redis server will use as well as which external IP addresses...