SQLIte mostly runs on slow CPU devices with relative fast SSDs. Reads are parallel, but writes are single threaded, so there is no advantage from multi core ARM CPUs.
The in-memory mode is also the default for many APIs. You can basically just use it like a collection for your language of choice but use SQL for putting and fetching things from the collection.
Not for the same database obviously, but SQLite databases are cheap. If your data can be split into different databases, you can pull off parallel writes.
