Neon has integrated support for PostgreSQL 15 into its storage system using Rust, allowing users to choose between PostgreSQL versions 14 and 15 when creating a Neon project. The integration involves using the Rust crate bindgen to generate Rust code from PostgreSQL's C headers, enabling the management of various PostgreSQL versions without code duplication. This process requires generating version-specific bindings for each PostgreSQL version and encapsulating them in separate submodules, which are accessed through functions that accept the version as a parameter. The approach ensures minimal changes to the existing codebase and simplifies the maintenance of PostgreSQL patches. Neon plans to expand support for more PostgreSQL extensions in future updates, encouraging community involvement through its online platform.