Why do so many programs use relation databases instead of loading the data during startup and keeping it in memory? Especially for smaller datasets I would think, that a database adds unnecessary complexity and overhead. Also, a lot of data can be saved using modern RAM and when using an in-memory approach, optimized data structures can be utilised to further improve the performance

Edit: yes I meant relational databases

I am currently looking for a multiroom speaker system which does not force me to place wiretap into my home. Also it should be able to simultaneously play the same song on multiple speakers. Which device can you recommend me? Best would be if no additional internet connection is necessary.