There has always been a case for server-side embedded databases for app servers. It can be an in-process library like SQLite or Apache Derby, but databases like

There has always been a case for server-side embedded databases for app servers. It can be an in-process library like SQLite or Apache Derby, but databases like SQL Anywhere and SQL Server also have local IPC protocols that achieve the same effect. App Embedded databases are not the main use case for non-SQL transactional engines like Berkeley DB and Microsoft ESE (used for ActiveDirectory and Exchange Server). SQLite is a better server-side engine than the critics think but it is ill suited with the default options. WAL mode and Shared Cache mode must be enabled for decent performance. The popular runtime libraries for SQLite don’t expose the required C API calls nor even the enhanced functionality of the FILE URL optional connection string. Even when configured properly, concurrency in SQLite is limited for apps that have a hot row or page. Row level locking or snapshot isolation are sometimes a huge help but fast local reads go a long way in alleviating the need. The main obstacle, however, is that the popular web frameworks assume a wire protocol SQL engine running on a separate tier like Heroku’s 12-Factor App architecture.