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SQLite does allow one to keep the entire database in memory: https://www.sqlite.org/inmemorydb.html

But is still orders of magnitude slower than a hash-map.

If you want ordering, then a hash-map doesn't help you.

Still orders of magnitude slower than a B-Tree Map.

You can also create an in-memory sqlite database though.

>The entire value proposition of Redis is that it operates out of memory

Not familiar with Redis specifically, but I doubt this idea. You can run anything on top of a ramdisk (granted, you can save a few pointer additions and get rid of some safety checks if you know you're working with memory)

Sure you can run things off a ramdisk, but the way you lay out data to achieve high performance from disk vs from RAM is different (disk assumes that you read pages of data at once, and tries to avoid reading extra pages, while RAM assumes that you read cache lines of data at once).

You can tun sqlite in memory by using the filename

:memory: