About 20 years ago, I worked on a server application that used mmap for its database. At startup, it read all the pages into memory, so all data was "hot", read

About 20 years ago, I worked on a server application that used mmap for its database. At startup, it read all the pages into memory, so all data was "hot", ready to go. It also built its in-memory indexes at the same time. It worked incredibly well, handling 1000's of simultaneous clients. This was the main enterprise application responsible for 100's of millions in revenue for a large organization. It wasn't a general purpose solution, though. The system also fed more standard relational databases for reporting purposes, using a custom change data capture process.