Quoting Fantastic Learning Resources under section "on larger programs"
Relational Database
Several components:
Storage engine, which stores data durably on disk and implements on-disk ordered data structures (B-tree or LSM)
Relational data model which is implemented on top of primitive ordered data structures.
Relational language to express schema and queries.
Either a TCP server to accept transactions as a database server, or an API for embedding for an in-processes “embedded” database.
Is there a good resource on building a rdbms in Rust ?