Netflix Open-Sources Quasar, a Cross-Repo Tool Tracking API Change Impact

Netflix disclosed Quasar, an internal tool that indexes symbol definitions and references across its repository ecosystem to measure the downstream impact of library changes¹. Built on the SCIP semantic code intelligence format, Quasar classifies symbols as added, removed, or signature-modified, then counts direct consumer references using Amazon Athena against Parquet data stored in Amazon S3. The tool indexes JVM, Go, Python, JavaScript/TypeScript, and Rust code and exposes findings through REST, GraphQL, and an MCP server. Netflix said Quasar reports observed impact without enforcing release policy, leaving decisions to library producers.