dgraph-io/badger ? reverse-engineered prompt

Build me a fast embedded key value database in Go that I can use inside my own app.

I want it to be persistent, pure Go, and optimized for SSDs, with a simple API for getting, setting, deleting, and iterating over keys in sorted order. It should support concurrent ACID transactions, snapshots, TTL, and versioned values, and I want a clean way to configure options like how much memory to use and how many versions to keep.

Also include the basic database maintenance stuff, like backup and restore, stream export and import, and a small command line tool for offline backup and restore. Make sure it has good tests, works reliably with crashes and filesystem weirdness, and is easy to install and use from another Go project.

If anything is unclear, check the current docs online and follow the existing behavior of Badger as closely as possible.