If you want 1 dependency rather than 0, there are various low-level libraries designed for building full-featured databases.

For one of these, RocksDB, one reference point is how CockroachDB was built on top of them for many years and many successful Jepsen tests (until they transitioned to an in-house solution).

https://www.cockroachlabs.com/blog/cockroachdb-on-rocksd/

https://www.cockroachlabs.com/blog/pebble-rocksdb-kv-store/

Another possibility is Apple's FoundationDB, with an interesting discussion here: https://news.ycombinator.com/item?id=37552085