Feature flags can be used not just over keywords like use, fn, mod etc. but inside the code logic itself, which SurrealDB makes extensive use of: https://github.com/surrealdb/surrealdb/blob/87da9c0b01c66de428887fc6560c19ad5efa0525/core/src/kvs/ds.rs#L210
For a quick intro to feature flags inside Cargo.toml, see the reference here: https://doc.rust-lang.org/cargo/reference/features.html
Install SurrealDB here: https://surrealdb.com/install?utm_source=youtube&utm_medium=social&utm_campaign=installation_page
