"Getting 50,000 Companies on Board with Clojure" by Cam Saul

Metabase successfully transitioned from Python to Clojure in 2014, with improved developer experience and deployment simplicity

The team consists of ~80 people (40 engineers), split between Clojure backend and JavaScript/TypeScript frontend developers

Key hiring insights:

• Clojure has been a selling point rather than barrier
• Successfully hired developers without prior Clojure experience
• Quality over quantity in candidate pool
• Remote-first with team members worldwide

Extensive use of tooling and custom solutions:

• CLJ-Kondo for linting and code quality
• Custom test runner (Hawk) built on top of eftest
• i18n framework with PO editor integration
• SQL parsing library (Macaw) for database compatibility
• Heavy use of Honey SQL 2 with custom extensions

Code quality maintained through:

• Extensive schema validation using Malli
• Custom linters and Kondo rules
• Strong emphasis on testing (6000+ tests)
• Automated enforcement of coding standards

Project scale:

• 1,600 Clojure source files
• 325,000 lines of Clojure code including tests
• Supporting numerous SQL databases and data sources
• Large open-source community engagement

Pragmatic approach to language adoption:

• Gradual transition strategies
• Mixed language environment (Clojure/JavaScript)
• Focus on developer productivity
• Emphasis on maintainable code

Benefits of choosing Clojure:

• Excellent JDBC library ecosystem
• JVM deployment simplicity
• Reduced framework churn compared to JavaScript
• Strong data processing capabilities