You can increase the size of a database's data page cache, which consists of the data pages kept in memory. When Derby can access a database page from the cache instead of reading it from disk, it can return data much more quickly.
In addition, you might want to prime all the caches in the background to make queries run faster when the user gets around to running them.
Prime this cache by selecting from much-used tables that are expected to fit into the data page cache.
The cache that holds information stored in the system tables. You can prime this cache with a query that selects from commonly used user tables.
The cache that holds database-specific Statements (including PreparedStatements). You can prime this cache by preparing common queries ahead of time in a separate thread.