Is it better to use an in-memory database (e.g. SQLite) than to keep everything in HashMap or other data structures?

Question

I need to have very fast access to a big Map - several millions of entries. Is it worth using an SQLite in-memory database to keep that map as opposed to just having that HashMap in memory?

Answer 1

its depends on the services you require from your data structure. do you only need to retrieve values from the map? or do you need to do a complex query or sorting?.

there is nothing magical about a database internal structure, to make it arbitrary faster then a simple data structure . In the database there are more facilities to manipulate large sets of data that probably will cost in an overheard of CPU and memory. if you only need a dictionary like functionality , go with a map, for something more complex consider a database